rt2800usb: remove PWR_PIN_CFG=0x3 during init

This seems to be only needed as workaround for hardware problem on
PCI devices.

Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>