kill CAR_GLOBAL_MIGRATION leftovers

Change-Id: Ia3b2c10af63cd0cab42dc39f479cb69bc4df9124
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37055
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/Kconfig

@@ -6,14 +6,6 @@ source "src/cpu/*/Kconfig"
 
 if ARCH_X86
 
-config CAR_GLOBAL_MIGRATION
-	bool
-	default n
-	help
-	  This option is selected if there is need to migrate CAR globals.
-	  All stages which use CAR globals can directly access the variables
-	  from their linked addresses.
-
 config DCACHE_RAM_BASE
 	hex