sata_sil24: fix kernel panic on ARM caused by unaligned access in sata_sil24

The sata_sil24 driver has six 16-bit registers that are initialised with
32-bit writes. This cause a kernel panic on ARM due to the unaligned
accesses which result.

This patch changes the accesses to the correct 16-bit ones.

Signed-off-by: Colin Tuckley <colin.tuckley@arm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>