Rather then open coding a cache of the vibra control registers use the
regmap cache code.  Also cache the interrupt mask register, providing
a small performance improvement for the interrupt code.
Signed-off-by: NMark Brown <broonie@linaro.org>
Acked-by: NPeter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>