EDAC, skx_edac: Delete duplicated code

Delete the duplicated code from skx_edac.c and rename skx_edac.c to
skx_base.c. Update the Makefile to build the skx_edac driver from
skx_base.c and skx_common.c.

Add SPDX to skx_base.c and clean out unnecessary #include lines.

 [ bp: Drop the license boilerplate - there's an SPDX identifier now. ]

Co-developed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: James Morse <james.morse@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: https://lkml.kernel.org/r/20190130191519.15393-4-tony.luck@intel.com