Bluetooth: btusb: Add the missed release_firmware() in btusb_mtk_setup_firmware()

[ Upstream commit d1e9d232e1e60fa63df1b836ec3ecba5abd3fa9d ]

btusb_mtk_setup_firmware() misses to call release_firmware() in an error
path. Jump to err_release_fw to fix it.

Fixes: f645125711c8 ("Bluetooth: btusb: fix up firmware download sequence")
Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>