gpio: omap: Get rid of pm_runtime_irq_safe()

If a gpio instance has any GPIO bits requested we do a pm_runtime_get()
on the device. Now with cpu_pm handling the deeper SoC idle state quirks,
let's just remove pm_runtime_irq_safe() call and add a warning in case we
ever happen to encounter it.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Keerthy <j-keerthy@ti.com>
Cc: Ladislav Michl <ladis@linux-mips.org>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>