claw: fix minor findings from code analysis tool

This patch fixes two problems in the claw driver identified by
static code analysis:
o Change in case differentiation of received sense codes
o Use correct data length in claw hard_start_xmit routine

Signed-off-by: Andrew H. Richter <richtera@us.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>