libbdplus: select libgcrypt in Config.in as well

Fixes http://autobuild.buildroot.org/results/4d9/4d91521378402f3f5b6402ea453df4c14c391bdc/

libbdplus adds libgcrypt to its _DEPENDENCIES, but forgot to select it in
Config.in.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libbdplus/Config.in

@@ -2,6 +2,7 @@ config BR2_PACKAGE_LIBBDPLUS
 	bool "libbdplus"
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on !BR2_STATIC_LIBS
+	select BR2_PACKAGE_LIBGCRYPT
 	help
 	  libbdplus is a research project to implement the BD+ System
 	  Specifications.