pata_amd: do not filter out valid modes in nv_mode_filter

On a Compaq Presario V3000 laptop (NVIDIA MCP51 chipset), pata_amd selects
PIO0 mode for the PATA DVD-RAM drive instead of MWDMA2 which it supports:

ata4.00: ATAPI: HL-DT-ST DVDRAM GSA-4084N, KQ09, max MWDMA2
ata4: nv_mode_filter: 0x39f&0x7001->0x1, BIOS=0x0 (0x0) ACPI=0x7001 (60:600:0x11)
ata4.00: configured for PIO0

For some reason, the BIOS-set UDMA configuration returns 0 and the ACPI _GTM
reports that UDMA2 and PIO0 are enabled. This causes nv_mode_filter to end up
allowing only PIO0 and UDMA0-2. Since the drive doesn't support UDMA we end up
using PIO0.

Since the controllers should always support PIO4, MWDMA2 and UDMA2 regardless
of what cable type is used, let's make sure we don't filter out these modes
regardless of what wacky settings the BIOS is using.

Signed-off-by: Robert Hancock <hancockrwd@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>