ibmvnic: Include missing return code checks in reset function

Check the return codes of these functions and halt reset
in case of failure. The driver will remain in a dormant state
until the next reset event, when device initialization will be
re-attempted.

Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>