kbuild: beautify the log of config whitelist check

Use the kbuild style log.

Prior to this commit:

./scripts/check-config.sh u-boot.cfg \
	./scripts/config_whitelist.txt . 1>&2

With this commit:

  CFGCHK  u-boot.cfg

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/scripts/check-config.sh b/scripts/check-config.sh
index 6618dfb..97e52dc 100755
--- a/scripts/check-config.sh
+++ b/scripts/check-config.sh
@@ -37,12 +37,12 @@
 	-e 's/^menuconfig \([A-Za-z0-9_]*\).*$/CONFIG_\1/p' |sort |uniq > ${ok}
 comm -23 ${suspects} ${ok} >${new_adhoc}
 if [ -s ${new_adhoc} ]; then
-	echo "Error: You must add new CONFIG options using Kconfig"
-	echo "The following new ad-hoc CONFIG options were detected:"
-	cat ${new_adhoc}
-	echo
-	echo "Please add these via Kconfig instead. Find a suitable Kconfig"
-	echo "file and add a 'config' or 'menuconfig' option."
+	echo >&2 "Error: You must add new CONFIG options using Kconfig"
+	echo >&2 "The following new ad-hoc CONFIG options were detected:"
+	cat >&2 ${new_adhoc}
+	echo >&2
+	echo >&2 "Please add these via Kconfig instead. Find a suitable Kconfig"
+	echo >&2 "file and add a 'config' or 'menuconfig' option."
 	# Don't delete the temporary files in case they are useful
 	exit 1
 else