hwaccess physmap: move x86 msr related code into own files

Allow x86 msr related code to be compiled independent from memory
mapping functionality. This enables for a better selection of needed
hardware access types.

Change-Id: Idc9ce9df3ea1e291ad469de59467646b294119c4
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/60111
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

meson.build

@@ -348,6 +348,7 @@ endif
 if need_raw_access
   srcs += 'hwaccess.c'
   srcs += 'hwaccess_x86_io.c'
+  srcs += 'hwaccess_x86_msr.c'
   srcs += 'physmap.c'
   cargs += '-DNEED_RAW_ACCESS=1'
   cargs += '-D__FLASHROM_HAVE_OUTB__=1'