Use vmalloc to allocate memory for the firmware image, and use a smaller
linear buffer for the actual transfer of the firmware to the chipset.

This patch is an adaptation of a similar patch for wl1251 by Kalle Valo.
Signed-off-by: NJuuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: NLuciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: NLuciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>