romstage_handoff: add helper to determine resume status

Instead of having callers query the romstage handoff resume
status by inspecting the object themselves add
romstage_handoff_is_resume() so that the same information
can be queried easily.

Change-Id: I40f3769b7646bf296ee4bc323a9ab1d5e5691e21
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/17647
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/skylake/chip_fsp20.c

@@ -35,13 +35,8 @@
 
 void soc_init_pre_device(void *chip_info)
 {
-	struct romstage_handoff *handoff;
-
-	/* Get S3 status to pass to silicon init. */
-	handoff = romstage_handoff_find_or_add();
-
 	/* Perform silicon specific init. */
-	fsp_silicon_init(handoff->s3_resume);
+	fsp_silicon_init(romstage_handoff_is_resume());
 }
 
 static void pci_domain_set_resources(device_t dev)