rom.sh: insert grub background in cbfs not memdisk

for some reason, when the background is in memdisk, inserting
it into cbfs afterward doesn't override, despite this
being the behaviour in grub.cfg

put it in cbfs explicitly, and skip inserting into memdisk

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/rom.sh

@@ -44,8 +44,7 @@ mkpayload_grub()
 	    --fonts= --themes= --locales=  --modules="$grub_modules" \
 	    --install-modules="$grub_install_modules" \
 	    "/boot/grub/grub_default.cfg=${srcdir}/.config" \
-	    "/boot/grub/grub.cfg=$grubdata/memdisk.cfg" \
-	    "/background.png=$grubdata/background/background1280x800.png" || \
+	    "/boot/grub/grub.cfg=$grubdata/memdisk.cfg" || \
 	    $err "$tree: cannot build grub.elf"; return 0
 }
 
@@ -163,6 +162,9 @@ add_grub()
 	printf "set grub_scan_disk=\"%s\"\n" "$grub_scan_disk" \
 	    > "$TMPDIR/tmpcfg" || $err "$target: !insert scandisk"
 	cbfs "$tmprom" "$TMPDIR/tmpcfg" scan.cfg raw
+	[ "$initmode" != "normal" ] && [ "$displaymode" != "txtmode" ] && \
+	    cbfs "$tmprom" "$grubdata/background/background1280x800.png" \
+	    "background.png" raw; :
 }
 
 mkseagrub()