libata: remove experimental tag on PATA drivers

Remove the experimental tag on Parallel ATA drivers. Though some of the
individual PATA drivers are still marked as experimental, as a group they can
hardly be considered to be, given they've been used in various distros for some
time.

Signed-off-by: Robert Hancock <hancockrwd@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>