ibmvnic: Fix error handling when registering long-term-mapped buffers

The patch stores the return code of the REQUEST_MAP_RSP sub-CRQ command
in the private data structure, where it can be later checked during
device open or a reset.

In the case of a reset, the mapping request to the vNIC Server may fail,
especially in the case of a partition migration. The driver attempts to
handle this by re-allocating the buffer and re-sending the mapping request.

The original error handling implementation was removed. The separate
function handling the REQUEST_MAP response message was also removed,
since it is now simple enough to be handled in the ibmvnic_handle_crq
function.

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