vboot2: Store depthcharge graphic assets only in RO

These files aren't updated (or updatable), and as such don't need to be
copied to the RW sections.

Change-Id: Ie78936792ad651fbf8500fc7e34f0899e33a904c
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/13633
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/vendorcode/google/chromeos/vboot2/Makefile.inc

@@ -95,4 +95,8 @@ regions-for-file = $(subst $(spc),$(comma),$(sort \
 			%/romstage) \
 		mts \
 		%/verstage \
+		locales \
+		locale_%.bin \
+		font.bin \
+		vbgfx.bin \
 		,$(1)),COREBOOT,COREBOOT FW_MAIN_A FW_MAIN_B)))