haswell: use s3_resume field in romstage_handoff

haswell: use s3_resume field in romstage_handoff

Now that there is a way to disseminate the presence of s3 wake more
formally use that instead of hard coded pointers in memory and stashing
magic values in device registers. The northbridge code picks up the
field's presence in the romstage_handoff structure and sets up the
acpi_slp_type variable accordingly.

Change-Id: Ida786728ce2950bd64610a99b7ad4f1ca6917a99
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2799
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>