spl: Makefile: include /config in the (reduced) FDT used by the SPL stage

When OF control is enabled for the SPL stage, nodes are removed from
the DTB to reduce its size. While /chosen is kept, /config is removed.

There's no reason why /chosen should be kept over /config (and as we
would like to put properties into /config that control the SPL stage),
we add '/config' to the list of nodes to be retained for the SPL stage.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Simon Glass <sjg@chromium.org>

scripts/Makefile.spl

@@ -232,7 +232,7 @@ fdtgrep_props := -b u-boot,dm-pre-reloc -b u-boot,dm-spl
 endif
 quiet_cmd_fdtgrep = FDTGREP $@
       cmd_fdtgrep = $(objtree)/tools/fdtgrep $(fdtgrep_props) -RT $< \
-		-n /chosen -O dtb | \
+		-n /chosen -n /config -O dtb | \
 	$(objtree)/tools/fdtgrep -r -O dtb - -o $@ \
 		$(addprefix -P ,$(subst $\",,$(CONFIG_OF_SPL_REMOVE_PROPS)))