media: dvb-usb: fix uninit-value in dvb_usb_adapter_dvb_init

If dibusb_read_eeprom_byte fails, the mac address is not initialized.
And nova_t_read_mac_address does not handle this failure, which leads to
the uninit-value in dvb_usb_adapter_dvb_init.

Fix this by handling the failure of dibusb_read_eeprom_byte.

Reported-by:  <syzbot+e27b4fd589762b0b9329@syzkaller.appspotmail.com>
Fixes: 786baecf ("[media] dvb-usb: move it to drivers/media/usb/dvb-usb")
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>