[media] media: video: mx2_camera.c: Provide error message if clk_get fails

Provide error message if clk_get fails.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>