ata: add Amiga Gayle PATA controller driver

Add Amiga Gayle PATA controller driver. It enables libata support
for the on-board IDE interfaces on some Amiga models (A600, A1200,
A4000 and A4000T) and also for IDE interfaces on the Zorro expansion
bus (M-Tech E-Matrix 530 expansion card).

Thanks to John Paul Adrian Glaubitz and Michael Schmitz for help
with testing the driver.

Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Michael Schmitz <schmitzmic@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Tejun Heo <tj@kernel.org>