mpc85xx: add user-space support for the TL-WDR4900 v1

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

git-svn-id: svn://svn.openwrt.org/openwrt@35733 3c298f89-4303-0410-b956-a3cf2f4a3e73