[media] s5p_cec: get rid of an unused var

drivers/staging/media/s5p-cec/s5p_cec.c: In function 's5p_cec_adap_enable':
drivers/staging/media/s5p-cec/s5p_cec.c:42:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
  int ret;
      ^~~

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>