In the error path, _request_firmware sets
firmware_p to NULL rather than *firmware_p,
which leads to passing a freed firmware
struct to drivers when the firmware file
cannot be found. Fix this.

Broken by commit f8a4bd34.
Reported-by: NWey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NPekka Enberg <penberg@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>