media: v4l: fwnode: C-PHY has no clock lane

C-PHY doesn't use a clock lane, hence the test for the clock lane when
there isn't one is faulty. Rework the test for the conflicting clock lane.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>