msi: Fix msi_remove_pci_irq_vectors.

Since msi_remove_pci_irq_vectors is designed to be called during
hotplug remove it is actively wrong to query the hardware and expect
meaningful results back.

To that end remove the pci_find_capability calls.  Testing
dev->msi_enabled and dev->msix_enabled gives us all of the information
we need.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>