CVE-2022-50537 firmware: raspberrypi: fix possible memory leak in rpi_firmware_probe()

In the Linux kernel, the following vulnerability has been resolved: firmware: raspberrypi: fix possible memory leak in rpifirmwareprobe In rpifirmwareprobe, if mboxrequestchannel fails, the 'fw' will not be freed through rpifirmwaredelete, fix this leak by calling kfree in the error path...