libata: pata_platform: make probe and remove functions device type neutral

Split pata_platform_{probe,remove} into two pieces:
1. pata_platform_{probe,remove} -- platform_device-dependant bits;
2. __ptata_platform_{probe,remove} -- device type neutral bits.

This is done to not duplicate code for the OF-platform driver.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Olof Johansson <olof@lixom.net>