crypto: nitrox - fix unchecked variable in nitrox_register_interrupts

Function nitrox_register_interrupts leaves variable 'nr_vecs' unchecked, which
would be use as kcalloc parameter later.

Fixes: 5155e118 ("crypto: cavium/nitrox - use pci_alloc_irq_vectors() while enabling MSI-X.")
Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>