Fix enable_irq_wake and disable_irq_wake symmetry in at91 pcmcia driver

disable_irq_wake call must be symmetric with enable_irq_wake.  This patch
fix that problem for the at91_pcmia driver.  It seems that this patch was
forgotten when we've fixed irq_wake symmetry in all at91 related drivers.
It was discussed in the "at91 drivers and [enable/disable]_irq_wake
(wrong?) usage" thread on the linux-arm-kernel mailing list.
Signed-off-by: Marc Pignat <marc.pignat@hevs.ch>
Cc: David Brownell <david-b@pacbell.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>