media: ov5640: Remove pixel clock rates

The pixel clock rates were introduced to report the initially static clock
rate.

Since this is now handled dynamically, we can remove them entirely.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Adam Ford <aford173@gmail.com> #imx6dq
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>