Revert "mb/google/rex: Create 64MB AP Firmware binary for Proto 0"

This reverts commit 1a8eb6c02103727431ac1ea23f4f507e49f3cde7.

Reason for revert: migrating to the 32MB AP Firmware hence, need to
revert this CL.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: Ibea1ad0cff008f9391cbda9e51899557b1e9c979
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67282
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tarun Tuli <taruntuli@google.com>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
diff --git a/src/mainboard/google/rex/Kconfig b/src/mainboard/google/rex/Kconfig
index 1286a79..c0f1b97 100644
--- a/src/mainboard/google/rex/Kconfig
+++ b/src/mainboard/google/rex/Kconfig
@@ -1,8 +1,6 @@
 config BOARD_GOOGLE_REX_COMMON
 	def_bool n
-	# FIXME: Rex Proto 0 only has 64MB SPINOR mounted on the board,
-	# and the plan is to use 32MB later with Proto 1 onwards.
-	select BOARD_ROMSIZE_KB_65536
+	select BOARD_ROMSIZE_KB_32768
 	select DRIVERS_GENERIC_MAX98357A
 	select DRIVERS_I2C_GENERIC
 	select DRIVERS_I2C_HID