On the at91sam9263, IRQs for GPIO banks C and D don't currently work.
This is because banks C, D, and E share one clock and toplevel IRQ, but
the AT91 code setting up and handling GPIO IRQs expects no sharing.
This patch:

 - Fixes GPIO IRQ setup and handling to cope with GPIO banks that are
   shared like on sam9263 chips, by setting up a list of those banks
   and making the IRQ dispatching logic scan that list.

 - Precomputes the address of each bank's registers, saving it with
   other per-bank data so that it no longer needs to be constantly
   recomputed during IRQs and other GPIO operations.  That shrinks
   hot-path code, while helping the GPIO bank irq updates.

 - Fixes a minor bug where IRQ_TYPE_NONE was wrongly rejected (it just
   means "use the default", which is "both edges" here).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>