[media] saa7134: Fix bytesperline not being set correctly for planar formats

bytesperline should be the bytesperline for the first plane for planar
formats, not that of all planes combined.

This fixes a crash in xawtv caused by the wrong bpl.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1305389


Reported-and-tested-by: Stas Sergeev <stsp@list.ru>

Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>