google/storm: romstage needs the accessor functions for buttons

In Chrome OS mode, the romstage tries to interpret the various buttons on the
device, so it needs access to the accessor functions.

Change-Id: I59a4f892ca84d475d8f46c8f8c1906dae10ad32d
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10704
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/mainboard/google/storm/Makefile.inc

@@ -31,6 +31,7 @@ verstage-y += reset.c
 
 romstage-y += romstage.c
 romstage-y += cdp.c
+romstage-y += chromeos.c
 romstage-y += mmu.c
 romstage-y += reset.c