V4L/DVB: saa7115: fix saa7111a support

When the saa7111 driver was merged into saa7115 several bugs were introduced,
in particular with the saa7111a support as is used in the mxb.c driver.
This patch fixes the saa7111a support. This was tested with the mxb driver.

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