ata: ahci_mvebu: a8040 a0: remove bad port register offsets workarounds

This workaround was added for A8040/7040 A0.
A8040/7040 A0 is no longer supported so this workaround
can be removed.

Signed-off-by: David Sniatkiwicz <davidsn@marvell.com>
Signed-off-by: Ken Ma <make@marvell.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Stefan Roese <sr@denx.de>