ARM: 7039/1: mach-davinci: move DaVinci TNET GPIO driver to GPIO subsystem

As per example from the other ARM boards, push the DaVinci TNET
GPIO driver down to the GPIO subsystem so it can be consolidated.

Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Kevin Hilman <khilman@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>