Patch from Andrew Victor

disable_irq() lazily disables the interrupt, so the IRQ is only disabled
once the interrupt occurs again.  The GPIO interrupt handler therefore
must first check disable_depth to see if the IRQ needs to be disabled.

Orignal patch by Bill Gatliff.
Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>