lotus,azalea: officially reserve the top 4096b of flash for SPI_FLAGS

Right now, the configuration storage support in
lotus/src/flash_storage.c claims overship of the top 0x1000 bytes of
flash and stores non-volatile configuration data in it.

However, the last 0x20 bytes of flash contain the RW_FWID (RW version)
section. In addition, RW_FW is specified as covering the entire top
0x40000 bytes of flash.

In short, flash looks roughly like this (not to scale)

+----------------------------------+-40000------------~----------------+
| RO_FW                            | RW_FW                             |
|                          RO_FRID |                           RW_FWID |
+----------------------------------+------------------~--------^-7FFE0-+

flash_storage can, if it grows large enough, corrupt the RW version
ID. If the RW firmware _also_ grows large enough, flash_storage can
overwrite part of it (!).

+----------------------------------+-40000------------~--+-7F000-------+
| RO_FW                            | RW_FW               |spi flag spi |
|                          RO_FRID |                     |flag Rp_ WlD |
+----------------------------------+------------------~--+-~---^-7FFE0-+

This change moves RW_FWID down to 0x7EFE0 and indicates in the FMAP that
the RW section can only occupy the top 0x3F000 bytes of flash.

The final layout looks more like this:

+----------------------------------+-40000----~----------+-7F000-------+
| RO_FW                            | RW_FW               |spi flag spi |
|                          RO_FRID |             RW_FWID |flag spi fla |
+----------------------------------+----------~--^-7EFE0-+-------------+

If the RW section grows too large for SPI flags, that will result in a
hard build break. That's probably better than runtime corruption of its
.text. :)

zephyr/program/lotus/azalea/overlay.dtsi

@@ -161,3 +161,22 @@
 	>;
 	pinctrl-names = "default";
 };
+
+&binman {
+	ec-rw {
+		/*
+		 * Azalea uses the last 0x1000 bytes of flash for non-volatile settings storage.
+		 * Shrink the RW region by that much so that there is no conflict between RW_FWID
+		 * or RW text and non-volatile settings.
+		 */
+		size = <0x3f000>;
+		rw-fw {
+			rw-fwid {
+				offset = <(0x3f000 - 32)>;
+			};
+		};
+	};
+	/* The remaining 0x1000 bytes will be used for non-volatile settings storage. */
+	pad-after = <0x1000>;
+	pad-byte = <0xFF>;
+};

zephyr/program/lotus/lotus/overlay.dtsi

@@ -139,3 +139,21 @@
 	pinctrl-names = "default";
 };
 
+&binman {
+	ec-rw {
+		/*
+		 * Lotus uses the last 0x1000 bytes of flash for non-volatile settings storage.
+		 * Shrink the RW region by that much so that there is no conflict between RW_FWID
+		 * or RW text and non-volatile settings.
+		 */
+		size = <0x3f000>;
+		rw-fw {
+			rw-fwid {
+				offset = <(0x3f000 - 32)>;
+			};
+		};
+	};
+	/* The remaining 0x1000 bytes will be used for non-volatile settings storage. */
+	pad-after = <0x1000>;
+	pad-byte = <0xFF>;
+};

zephyr/program/lotus/program.conf

@@ -16,6 +16,7 @@ CONFIG_PLATFORM_EC_SYSTEM_UNLOCKED=y
 CONFIG_PLATFORM_EC_WP_DISABLE=y
 CONFIG_PLATFORM_EC_UNIMPLEMENTED_GPIO=y
 CONFIG_PLATFORM_EC_I2C_DEBUG=y
+CONFIG_CROS_EC_RW_SIZE=0x3F000
 
 # Port80
 CONFIG_PLATFORM_EC_PORT80_4_BYTE=y