[libata] ata_tf_to_host cleanups

Integrate ata_exec() and ata_tf_to_host() into their only caller,
ata_bus_edd().

Rename ata_tf_to_host_nolock() to ata_tf_to_host().

This makes locking a bit easier to review, and may help pave the way for
future changes.
2 files changed