irqdesc: Add a resource managed version of irq_alloc_descs()

Add a devres flavor of __devm_irq_alloc_descs() and corresponding
helper macros.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-doc@vger.kernel.org
Cc: Jonathan Corbet <corbet@lwn.net>
Link: http://lkml.kernel.org/r/1486729403-21132-1-git-send-email-bgolaszewski@baylibre.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>