[PATCH] sky2: msi enhancements.

If using Message Signaled Interrupts (MSI) then the IRQ will never
be shared. Don't call pci_disable_msi() unless using MSI.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>