It is possible that on one of the error paths we are going to try to free
'rxbuf', even though it has not been allocated yet, which cause the following
warning:
drivers/staging/iio/adc/max1363_ring.c: In function 'max1363_trigger_handler':
drivers/staging/iio/adc/max1363_ring.c:87:7: warning: 'rxbuf' may be used
uninitialized in this function