coreboot: gru: Use default coreboot tree

We don't really need a custom coreboot tree for Chromebooks. I had added
one, because at a cursory glance to the available config/coreboot/board
subdirectories I had the impression that I should. But upstreams have
one tree for every board and I think we should move towards that too.

Move the one important BL31 makefile patch into the default coreboot
patches, update the gru boards' configs by running savedefconfig in the
cros tree and then running olddefconfig in the default tree.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

script/update/project/trees

@@ -196,9 +196,7 @@ check_cross_compiler()
 
 	cbdir="src/coreboot/${tree}"
 	[ "${project}" != "coreboot" ] && \
-		cbdir="src/coreboot/default" # not u-boot (e.g. linux)
-	[ "${project}" = "u-boot" ] && \
-		cbdir="src/coreboot/cros" # u-boot only used on coreboot/cros
+		cbdir="src/coreboot/default"
 
 	# only true if not building coreboot:
 	ctarget="${cbdir#src/coreboot/}"