base-files: define yes/no as valid boolean options

ubox validate_data defines yes/no as valid boolean options, do the same in
config_get_bool too.

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41405 3c298f89-4303-0410-b956-a3cf2f4a3e73
mvebu: drop 3.10 support

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41406 3c298f89-4303-0410-b956-a3cf2f4a3e73