sky2: Disable MSI on P5W DH Deluxe

The onboard sky2 NICs send IRQs after S3, resulting in ethernet not
working after resume.
Maskable MSI and MSI-X are also not supported, so fall back to INTx.

Signed-off-by: Tasos Sahanidis <tasos@tasossah.com>
Signed-off-by: David S. Miller <davem@davemloft.net>