wl1251: fix a memory leak in probe

wl1251_sdio_probe() error path is missing wl1251_free_hw, add it.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Acked-by: Kalle Valo <kvalo@adurom.com>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>