sh_mobile_ceu_camera: Fix a compilation warning

drivers/media/platform/soc_camera/sh_mobile_ceu_camera.c: In function 'sh_mobile_ceu_clock_start':
drivers/media/platform/soc_camera/sh_mobile_ceu_camera.c:613:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]

Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>