cpu/x86/Kconfig.debug_cpu: Drop unused symbol

Change-Id: I2b611773e596bea4788b05a3f58485fb3e002402
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69362
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>

src/cpu/x86/Kconfig.debug_cpu

@@ -1,12 +1,5 @@
 if ARCH_X86
 
-config HAVE_DEBUG_CAR
-	bool
-
-config DEBUG_CAR
-	bool "Output verbose Cache-as-RAM debug messages"
-	depends on HAVE_DEBUG_CAR
-
 config DISPLAY_MTRRS
 	bool "Display intermediate MTRR settings"