drivers/intel/fsp2_0: Hide the Kconfig option to run FSP-M XIP

This is a property of the FSP, not something the user can decide.

Change-Id: I2086e67d39e88215ee0f124583b810f7df072f80
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36170
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michael Niewöhner
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/drivers/intel/fsp2_0/Kconfig

@@ -103,7 +103,7 @@ config FSP_CAR
 	  Use FSP APIs to initialize & Tear Down the Cache-As-Ram
 
 config FSP_M_XIP
-	bool "Is FSP-M XIP"
+	bool
 	default n
 	help
 	  Select this value when FSP-M is execute-in-place.