pata_via: clean up recent tf_load changes

Commit bfce5e0179ad059035df28558724ff60af708e09 implemented custom
tf_load for pata_via.  This patch cleans it up a bit.

* Instead of duplicating whole body, copy tf and set ATA_TFLAG_DEVICE
  when necessary.

* Rename via_ata_tf_load() to via_tf_load().

* No need to set .tf_load in via_port_ops_noirq as it inherits from
  via_port_ops.

* Clean up indentation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Joseph Chan <JosephChan@via.com.tw>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>