soc/intel/skylake: Add option to control microcode update inclusion

soc/intel/skylake: Add option to control microcode update inclusion

On embedded boards the cpu mounted on the board is known. So it is not
required to include microcode for all possible Sky Lake and Kaby Lake
cpus. This patch provides the possibility to only support the versions
required.

By default all microcode updates will be included and the versions not
required can be removed using Kconfig.

BUG=N/A
TEST=build

Change-Id: Iaa36c2846b2279a2eb2b61e6c97d6c89d0736f55
Signed-off-by: Wim Vervoorn <wvervoorn@eltan.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37514
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>