bnx2: Flush the register writes which setup the MSI-X table

The MSI-X table size needs to be properly set before pci_enable_msix()
is called.  But on certain machines, the writes are delayed and the
MSI-X table size is incorrectly read.  By reading the
BNX2_PCI_MSIX_CONTROL register, the writes are flushed and now
ensure that the MSI-X table is set correctly before MSI-X
is enable on the device.

This patch was originally diagnosed and authored by
Kalyan Ram Chintalapati <kalyanc@vmware.com>.

Signed-off-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: Kalyan Ram Chintalapati <kalyanc@vmware.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>