cpu/intel/*/Kconfig: move selection of CPU_X86_CACHE_HELPER

Move the selection of CPU_X86_CACHE_HELPER to the Kconfig file of the
CPU models which call the x86_enable_cache function that gets added to
the build by selecting this option.

Change-Id: Ie75682f5d20a79fc2f3aab9b8a2c3ccf79d1ad5c
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44227
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/cpu/intel/socket_m/Kconfig

@@ -7,7 +7,6 @@ config SOCKET_SPECIFIC_OPTIONS
 	def_bool y
 	select CPU_INTEL_MODEL_6EX
 	select CPU_INTEL_MODEL_6FX
-	select CPU_X86_CACHE_HELPER
 	select MMX
 	select SSE