pata_hpt{37x|3x2n}: SATA mode filtering

The Marvell bridge chips used on HighPoint SATA cards do not seem to support
the UltraDMA modes 1, 2, and 3 as well as any MWDMA modes;  these cards are
based on HPT372/372A/372N/374 chips (judging from the vendor drivers), so
the Linux drivers need to have a mode_filter() method for these chips...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>