wl12xx: fix spelling

Changes (comments and debug output):
* couldnt -> couldn't
* frmware -> firmware
* recevied -> received

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Acked-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>