ARM: mxc: Add missing lockdep annotation

The irq_set_wake() function of the gpio irq_chip calls
enable/disable_irq_wake() on the demultiplex interrupt. That leads to
a lockdep warning "INFO: possible recursive locking detected" because
irq_set_type() is called under irq_desc->lock and the *_irq_wake()
calls take irq_desc->lock of the demux interrupt.

Tell lockdep that the gpio irqs are in a different lock class.

Documentation/SubmitChecklist:
 15: All codepaths have been exercised with all lockdep features enabled.

That's a non-optional requirement, AFAICT.

Reported-and-tested-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LAKML-Reference: alpine.LFD.2.00.1104041416290.19945@localhost6.localdomain6
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>