Although it should be unnecessary, add a NULL pointer check
to trf7970a_send_upstream() to eliminate a smatch warning.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NMark Greer <mgreer@animalcreek.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>