[MIPS] Add generic GPIO to Au1x00

This patch adds support for the generic GPIO API to Au1x00 boards. It requires
the generic GPIO patch for MIPS boards by Yoichi Yuasa. Now there is a MIPS
target using it, can you queue these patchset for 2.6.22 ? Thank you very
much in advance.

Signed-off-by: Florian Fainelli <florian.fainelli@telecomint.eu>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>