media: saa7134: fix saa7134_initdev error handling logic

Smatch reported an issue there:
	drivers/media/pci/saa7134/saa7134-core.c:1302 saa7134_initdev() warn: '&dev->devlist' not removed from list

But besides freeing the list, the media controller graph also
needs to be cleaned up on errors. Address those issues.

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