claw: remove unused return code handling

Remove unused return code handling. The claw driver is mostly dead, so
just make sure it keeps compiling without warnings.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>