arm: ep93xx: Add basic interrupt info

For the time being can we fix up the ep93xx gpio code with the amended
patch below. It keeps the information that the pin is also configured
as an interrupt and cleans the code up a bit.

[ tglx: Rebased it on the removal patch ]

Signed-off-by: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>