ARM: omap: update GPIO chained IRQ handler to use entry/exit functions

This patch updates the OMAP gpio chained IRQ handler to use the chained
IRQ enter/exit functions in order to function correctly on primary
controllers with different methods of flow control.

Cc: Colin Cross <ccross@google.com>
Cc: Tony Lindgren <tony@atomide.com>
Tested-and-acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>