Currently the OMAP GPIO driver uses a legacy mapping for the GPIO IRQ
domain. This is not necessary because we do not need to assign a
specific interrupt number to the GPIO IRQ domain. Therefore, convert
the OMAP GPIO driver to use a linear mapping instead.

Please note that this also allows to simplify the logic in the OMAP
gpio_irq_handler() routine, by using irq_find_mapping() to obtain the
virtual irq number from the GPIO bank and bank index.
Reported-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NJon Hunter <jon-hunter@ti.com>
Reviewed-by: NFelipe Balbi <balbi@ti.com>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: NKevin Hilman <khilman@linaro.org>
Tested-by: NJavier Martinez Canillas <javier@dowhile0.org>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>