romstage_handoff: add s3_resume field

Provide a field in the romstage_handoff structure to indicate if the
current boot is an ACPI S3 wake boot. There are currently quite a few
non-standardized ways of passing this knowledge to ramstage from
romstage. Many utilize stashing magic numbers in device-specific
registers. The addition of this field adds a more formalized method
passing along this information. However, it still requires the romstage
chipset code to initialize this field. In short, this change does not
make this a hard requirement for ramstage.

Change-Id: Ia819c0ceed89ed427ef576a036fa870eb7cf57bc
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2796
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/romstage_handoff.h

@@ -31,6 +31,8 @@ struct romstage_handoff {
 	/* This indicates to the ramstage to reserve a chunk of memory. */
 	uint32_t reserve_base;
 	uint32_t reserve_size;
+	/* Inidicate if the current boot is an S3 resume. */
+	uint32_t s3_resume;
 };
 
 #if defined(__PRE_RAM__)