vboot: Remove rmu.bin from FW_MAIN_A and FW_MAIN_B

Add rmu.bin to the list of files that exist only in the read-only
section (COREBOOT) of the SPI flash.

TEST=Build and run on Galileo Gen2.

Change-Id: I30cbd3fb2ef1848807e4de4c479dc7a561c1faba
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-on: https://review.coreboot.org/18031
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/vboot/Makefile.inc b/src/vboot/Makefile.inc
index 33109de..c03d639 100644
--- a/src/vboot/Makefile.inc
+++ b/src/vboot/Makefile.inc
@@ -152,6 +152,7 @@
 		locale_%.bin \
 		font.bin \
 		vbgfx.bin \
+		rmu.bin \
 		,$(1)),COREBOOT,COREBOOT FW_MAIN_A FW_MAIN_B)))
 
 endif # CONFIG_VBOOT