brcmfmac: use firmware data buffer directly for nvram

The nvram file could be parsed directly in the data buffer in the
firmware structure passed by request_firmware function. This patch
gets rid of the redundant memcpy.

Reviewed-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>