brcmfmac: Loading the correct firmware for brcm43456

SDIO based brcm43456 is currently misdetected as brcm43455 and the wrong
firmware name is used. Correct the detection and load the correct
firmware file. Chiprev for brcm43456 is "9".

Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>