spmi/pmic: Use irq_desc_get_xxx() to avoid redundant lookup of irq_desc

Use irq_desc_get_xxx() to avoid redundant lookup of irq_desc while we
already have a pointer to corresponding irq_desc.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: http://lkml.kernel.org/r/20150713151750.915477120@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>