Fix unused variable build errors.

This patch fixes these build errors on CentOS 6.

  CC	net/caif_setsockopt.o
cc1: warnings being treated as errors
net/caif_setsockopt.c: In function ‘caif_setsockopt’:
net/caif_setsockopt.c:20: error: unused variable ‘val’

  CC	net/rds_setsockopt.o
cc1: warnings being treated as errors
net/rds_setsockopt.c: In function ‘rds_setsockopt’:
net/rds_setsockopt.c:23: error: unused variable ‘val’

Signed-off-by: Vinson Lee <vlee@twitter.com>