ar71xx: enable LEDs on Hornet-UB X2

None of the LEDs are enabled by default on the Hornet-UB X2 board
(the 16/64MB version of the Hornet-UB), because it uses a different
board-name ("hornet-ub-x2"); but hornet-ub and hornet-ub-x2 boards
are equivalent WRT their LEDs.

SIgned-off-by: Joshua Judson Rosen <jrosen@harvestai.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@45328 3c298f89-4303-0410-b956-a3cf2f4a3e73