mb/facebook/monolith: Don't override `CBFS_SIZE` prompt

Change-Id: I6fac40918f1ca3227ff68e79fcae039a26356d0d
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56550
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by:  Felix Singer <felixsinger@posteo.net>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/facebook/monolith/Kconfig

@@ -14,7 +14,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select VPD
 
 config CBFS_SIZE
-	hex "CBFS_SIZE"
+	hex
 	default 0x00900000
 
 config IRQ_SLOT_COUNT