ata: constify of_device_id structures

Declare of_device_id structures as const as they are either passed to
the macro MODULE_DEVICE_TABLE or stored in the of_match_table field of a
device_driver structure. This field is of type const, so of_device_id
structures having this property can be made const too.

Cross compiled the files drivers/ata/pata_macio.c and
drivers/ata/pata_mpc52xx.c for powerpc architecture.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>