Add support for storing POST codes in CMOS

This will use 3 bytes of CMOS to keep track of the POST
code for the current boot while also leaving a record of
the previous boot.

The active bank is switched early in the bootblock.

Test:
1) clear cmos
2) reboot
3) use "mosys nvram dump" to verify that the first byte
contains 0x80 and the second byte contains 0xF8
4) powerd_suspend and then resume
5) use "mosys nvram dump" to verify that the first byte
contains 0x81 and the second byte contains 0xFD

Change-Id: I1ee6bb2dac053018f3042ab5a0b26c435dbfd151
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/1743
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/src/arch/x86/init/bootblock_simple.c b/src/arch/x86/init/bootblock_simple.c
index 41f73b4..fd9ba22 100644
--- a/src/arch/x86/init/bootblock_simple.c
+++ b/src/arch/x86/init/bootblock_simple.c
@@ -10,6 +10,9 @@
 #if CONFIG_USE_OPTION_TABLE
 		sanitize_cmos();
 #endif
+#if CONFIG_CMOS_POST
+		cmos_post_init();
+#endif
 	}
 
 	const char* target1 = "fallback/romstage";