mpc85xx-p1010: add support for Enterasys WS-AP3715i (#2993)

Enterasys WS-AP3715i is a dualband wireless-N access point.
It comes in a similar casing as the WS-AP3825i, however the hardware is
fundamentally different from its bigger cousin.

Signed-off-by: David Bauer <mail@david-bauer.net>