update-defconfigs.sh: use buildroot config util

Take advantage of buildroot/utils/config to perform mass changes that
are specified as arguments to this script, before running olddefconfig +
savedefconfig. The syntax is the same as the config config script, just
omitting the --file argument. Example usage:

$ openpower/scripts/update-defconfigs.sh \
    --enable LINUX_KERNEL_CUSTOM_VERSION \
    --set-str LINUX_KERNEL_CUSTOM_VERSION_VALUE "5.5"

Additionally, actually make the script executable.

Signed-off-by: Klaus Heinrich Kiwi <klaus@linux.vnet.ibm.com>
diff --git a/openpower/scripts/update-defconfigs.sh b/openpower/scripts/update-defconfigs.sh
old mode 100644
new mode 100755
index c82900c..f51fc8f
--- a/openpower/scripts/update-defconfigs.sh
+++ b/openpower/scripts/update-defconfigs.sh
@@ -10,6 +10,9 @@
 	echo $PLATFORM
 	ODIR=`mktemp -d`
 	op-build O=$ODIR $PLATFORM_DEFCONFIG
+	if [ $# -gt 0 ]; then
+		buildroot/utils/config --file $ODIR/.config "$@"
+	fi
 	op-build O=$ODIR olddefconfig
 	op-build O=$ODIR savedefconfig
 	rm -rf $ODIR