[media] media: i2c: lm3560: fix missing unlock on error in lm3560_set_ctrl()

Add the missing unlock before return from function lm3560_set_ctrl()
in the error handling case.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>