sdk: provide explicit CONFIG_MODULES kconfig symbol

Extend the SDK Config.in file to explicitely declare a MODULES symbol with
the "option modules" flag set in order to prevent a kconfig segmentation fault
whenever a "depends m" dependency is encountered.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

SVN-Revision: 46514

target/sdk/files/Config.in

@@ -1,2 +1,7 @@
+config MODULES
+	bool
+	default y
+	option modules
+
 source "Config-build.in"
 source "tmp/.config-package.in"