gpio/omap: maintain GPIO and IRQ usage separately

commit fa365e4d729065b5e85165df3dc9699ed47489cc upstream.

The GPIO OMAP controller pins can be used as IRQ and GPIO
independently so is necessary to keep track GPIO pins and
IRQ lines usage separately to make sure that the bank will
always be enabled while being used.

Also move gpio_is_input() definition in preparation for the
next patch that setups the controller's irq_chip driver when
a caller requests an interrupt line.

Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: George Cherian <george.cherian@ti.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Tested-by: Lars Poeschel <poeschel@lemonage.de>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>