wifi: rtw89: uninitialized variable on error in rtw89_early_fw_feature_recognize()

If request_partial_firmware_into_buf() fails then "firmware" is not
initialized and the release_firmware(firmware) will crash.

Fixes: deebea35 ("wifi: rtw89: early recognize FW feature to decide if chanctx")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/YyMzDtX/3fUBnonC@kili