arch/x86: move postcar main logic into C

The console_init(), MTRR printing, and loading ramstage
logic was previously all in assembly. Move that logic
into C code so that future features can more easily be
added into the postcar boot flow.

BUG=chrome-os-partner:57513

Change-Id: I332140f569caf0803570fd635d894295de8c0018
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16618
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/arch/x86/Makefile.inc

@@ -287,6 +287,7 @@ postcar-y += memmove.c
 postcar-y += memset.c
 postcar-y += memlayout.ld
 postcar-$(CONFIG_X86_TOP4G_BOOTMEDIA_MAP) += mmap_boot.c
+postcar-y += postcar.c
 postcar-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
 
 LDFLAGS_postcar += -Map $(objcbfs)/postcar.map