MSI: Add an arch_msi_check_device()

Add an arch_check_device(), which gives archs a chance to check the input
to pci_enable_msi/x. The arch might be interested in the value of nvec so
pass it in. Propagate the error value returned from the arch routine out
to the caller.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>