gpio/omap: convert gpio irq domain to linear mapping

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: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
gpio/omap: warn if bank is not enabled on setting irq type

For OMAP devices, if a gpio is being used as an interrupt source but has
not been requested by calling gpio_request(), a call to request_irq()
may cause the kernel hang because the gpio bank may be disabled and
hence the register access will fail. To prevent such hangs, test for
this case and warn if this is detected.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Merge branch 'cleanup-timer' into daily-testing

* cleanup-timer:
  ARM: OMAP4+: Fix sparse warning in system timers
  ARM: OMAP2+: Store ID of system timers in timer structure
  ARM: OMAP3: Update clocksource timer selection
  ARM: OMAP2+: Simplify system timers definitions
  ARM: OMAP2+: Simplify system timer clock definitions
  ARM: OMAP2+: Remove hard-coded test on timer ID
  ARM: OMAP2+: Display correct system timer name
Merge branch 'fixes-gpio' into daily-testing

* fixes-gpio:
  gpio/omap: warn if bank is not enabled on setting irq type
  gpio/omap: convert gpio irq domain to linear mapping