media: dvbdev: fix error logic at dvb_register_device()

As reported by smatch:

	drivers/media/dvb-core/dvbdev.c: drivers/media/dvb-core/dvbdev.c:510 dvb_register_device() warn: '&dvbdev->list_head' not removed from list
	drivers/media/dvb-core/dvbdev.c: drivers/media/dvb-core/dvbdev.c:530 dvb_register_device() warn: '&dvbdev->list_head' not removed from list
	drivers/media/dvb-core/dvbdev.c: drivers/media/dvb-core/dvbdev.c:545 dvb_register_device() warn: '&dvbdev->list_head' not removed from list

The error logic inside dvb_register_device() doesn't remove
devices from the dvb_adapter_list in case of errors.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>