firmware: raspberrypi: fix possible memory leak in rpi_firmware_probe()

firmware: raspberrypi: fix possible memory leak in rpi_firmware_probe()

In rpi_firmware_probe(), if mbox_request_channel() fails, the 'fw' will
not be freed through rpi_firmware_delete(), fix this leak by calling
kfree() in the error path.

Fixes: 1e7c57355a3b ("firmware: raspberrypi: Keep count of all consumers")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221117070636.3849773-1-yangyingliang@huawei.com
Acked-by: Joel Savitz <jsavitz@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>