scsi: fnic: fix msix interrupt allocation

pci_alloc_irq_vectors() returns number of vectors allocated.  Fix the check
for error condition.

Fixes: cca678df

 ("scsi: fnic: switch to pci_alloc_irq_vectors")
Link: https://lore.kernel.org/r/20190827211340.1095-1-gvaradar@cisco.com
Signed-off-by: Govindarajulu Varadarajan <gvaradar@cisco.com>
Acked-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>