GPIO: add new Xilinx driver for powerpc

This driver supports the Xilinx XPS GPIO IP core which has the typical
GPIO features.

Signed-off-by: Kiran Sutariya <kirans@xilinx.com>
Signed-off-by: John Linn <john.linn@xilinx.com>
Cc: David Brownell <david-b@pacbell.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Kumar Gala <galak@gate.crashing.org>
Cc: "Grant Likely" <grant.likely@secretlab.ca>
Cc: <avorontsov@ru.mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>