fnic: pci_dma_mapping_error() doesn't return an error code

pci_dma_mapping_error() returns true on error and false on success.

Fixes: fd6ddfa4

 ('fnic: check pci_map_single() return value')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>