prism54: support for 124a:4025 - another version of IOGear GWU513 802.11g

Add support to p54usb driver for apparently another version of IOGear GWU513
802.11g USB network card that uses GW3887IK chipset and is recognized as
"124a:4025 AirVast" by lsusb.

Cc: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>