[ARM] 4848/1: at91: remove false lockdep warnings

Remove false lockdep warnings about lock recursion when declaring
IRQs as being wake-capable, by marking putting GPIO irq_desc locks
into their own class.

(Thanks to Peter Zijlstra for helping track down such a small
fix to this problem.)

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>