V4L/DVB (8940): saa7115: fix saa7111(a) support

The saa7111 support in saa7115.c was missing some features and did not
properly take some of the differences into account. With this patch
saa7115 can be used in the mxb driver instead of saa7111.c.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>