[media] v4l2-clk: v4l2_clk_get() also need to find the of_fullname clock

The soc-camera host will be probed and register a v4l2_clk, but if at
that moment, the i2c device is not available, then the registered
v4l2_clk name is an OF string not a I2C string.

So when i2c sensor probes and calls v4l2_clk_get(), it only searches a
clock with I2C string, like "1-0030".

This patch will search the clock with OF string name if no clock with
I2C string name could be found.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>