ar71xx: add a generic GPIO latch driver

It will be used for the Mikrotik boards.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39697 3c298f89-4303-0410-b956-a3cf2f4a3e73
ar71xx/mikrotik: enable the GPIO latch driver

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39698 3c298f89-4303-0410-b956-a3cf2f4a3e73
ar71xx: rb91x: register a gpio-latch platform device

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39699 3c298f89-4303-0410-b956-a3cf2f4a3e73