[media] as3645a: Add driver for LED flash controller

This patch adds the driver for the as3645a LED flash controller. This
controller supports a high power led in flash and torch modes and an
indicator light, sometimes also called privacy light.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Nayden Kanchev <nkanchev@mm-sol.com>
Signed-off-by: Tuukka Toivonen <tuukkat76@gmail.com>
Signed-off-by: Antti Koskipaa <antti.koskipaa@gmail.com>
Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Vimarsh Zutshi <vimarsh.zutshi@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: Mika Westerberg <ext-mika.1.westerberg@nokia.com>
Signed-off-by: David Cohen <dacohen@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>