ata_piix: update map 10b for ich8m

Fix map entry 10b for ich8.  It's [P0 P2 IDE IDE] like ich6 / ich6m.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: <Kristen Carlson Accardi> kristen.c.accardi@intel.com
Signed-off-by: Jeff Garzik <jeff@garzik.org>