vxge: Fixed MSIX interrupt configuration.

- Fixed MSIX interrupt configuration to support non contiguous vpaths in
  functions. Four msi-x vectors are reserved per vpath internal to the chip.
  In all, there are 68 msi-x vectors for the 17 vpaths in the chip. In the
  multi function configurations, non-contiguous vpaths are configured to
  represent a function. For instance vpaths 0 and 8 can be configured to
  represent function zero.

- If pci_enable_msix fails for the requested vectors, try with a lesser number
  vectors by reducing the vpath count.

Signed-off-by: Sreenivasa Honnur <sreenivasa.honnur@neterion.com>
Signed-off-by: Ramkrishna Vepa <ram.vepa@neterion.com>
Signed-off-by: David S. Miller <davem@davemloft.net>