Omap no longer needs this option, mach/gpio.h is
empty.

Also remove mach/irqs.h from gpio-omap.h and
include it directly from the related omap1
gpio init files.

Otherwise omap2+ build fails for MULTI_PLATFORM.

Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Jarkko Nikula <jarkko.nikula@bitmer.com>
Cc: Liam Girdwood <lrg@ti.com>
Cc: alsa-devel@alsa-project.org
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>