V4L/DVB (12159): soc_camera: Fix debug output of supported formats count

The supported formats count must be set to 0 after debug output
right before the second pass.

Signed-off-by: Stefan Herbrechtsmeier <hbmeier@hni.uni-paderborn.de>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>