gpio: gpio-omap: configure edge detection for level IRQs for idle wakeup

The GPIO block can enter idle independently of the CPU power management
calls via smart-idle.  When the GPIO block enters idle, level detection
stops working due to clocks being shut off, and an alternative form of
edge detection is used.  However, this needs the edge detection
registers set to mark the appropriate edges.

Arrange to configure the edge detection enables along with the level
detection to ensure that any transition to active interrupt state that
occurs while the block is idle is detected as a wake-up event.

Since we enable the edge detection when configuring the IRQ, both
omap2_gpio_enable_level_quirk() nor omap2_gpio_disable_level_quirk()
become redundant, which also means OMAP_GPIO_QUIRK_IDLE_REMOVE_TRIGGER
can be removed. This can be now done without regressions as patch
"gpio: gpio-omap: fix level interrupt idling" allows level interrupts
to idle on omap4 without a workaround.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Keerthy <j-keerthy@ti.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
[tony@atomide.com: update description for the fix dependency]
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>