i82801gx: Fix port status in AHCI mode

i82801gx: Fix port status in AHCI mode

The code used PCI register 0x92 to enable sata ports,
which is wrong. The ICH7 documentation states:

"This register is only used in systems that do not
support AHCI. In AHCI enabled systems, bits[3:0] must
always be set (ICH7R only) / bits[2,0] must always be set
(Mobile only), and the status of the port is controlled
through AHCI memory space."

Writing 0x0f to ICH7-M doesn't seem to hurt, so lets write
0x0f for both variants. This patch makes sata_ahci work on
my Thinkpad T60 and X60s.

Change-Id: If3b3daec2e5fbaa446de00272ebde01cd8d52475
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Reviewed-on: http://review.coreboot.org/340
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>