sata_mv: cosmetic renames

Add _OFS suffix to more of the register offset names,
for consistency with the rest of the driver.

Also tag the defines for LTMODE and PHY_MODE4 to note
that read-after-write is necessary when updating those regs.

No code changes here.

[NOTE: this commit is undone a few commits later]

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>