wl1271: Changed platform_device to be dynamically allocated

Changed platform_device to be allocated dynamically from the
wl1271_alloc_hw function. Also cleaned up error handling in the
wl1271_alloc_hw function and module probe functions.

Signed-off-by: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>