media: ARM: dts: imx6qdl-pico: Drop clock-names property

Now that the driver has been updated to drop fetching the clk reference by
name we no longer need the clock-names property in the ov5645 sensor node.

This is in preparation for removal for clock-names property from the
DT binding.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>