sky2: Disable MSI on ASUS P6T

The onboard sky2 NIC on ASUS P6T WS PRO doesn't work after PM resume
due to the infamous IRQ problem.  Disabling MSI works around it, so
let's add it to the blacklist.

Unfortunately the BIOS on the machine doesn't fill the standard
DMI_SYS_* entry, so we pick up DMI_BOARD_* entries instead.

BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1142496
Reported-and-tested-by: Marcus Seyfarth <m.seyfarth@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>