Calculate the exact number of vectors we'll use before calling
pci_alloc_msix. Don't grab nine all the time.
Call cxgb_setup_interrupts once per T3, not once per port. Ditto
for cxgb_teardown_interrupts.
Don't leak resources when interrupt setup fails in the middle.
Obtained from: Navdeep Parhar
MFC after: 10 days