iio: light: add APDS9960 ALS + promixity driver

APDS9960 is a combination of ALS, proximity, and gesture sensors.

This patch adds support for these functions along with gain control,
integration time, and event thresholds.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/Makefile

@@ -7,6 +7,7 @@ obj-$(CONFIG_ACPI_ALS)		+= acpi-als.o
 obj-$(CONFIG_ADJD_S311)		+= adjd_s311.o
 obj-$(CONFIG_AL3320A)		+= al3320a.o
 obj-$(CONFIG_APDS9300)		+= apds9300.o
+obj-$(CONFIG_APDS9960)		+= apds9960.o
 obj-$(CONFIG_BH1750)		+= bh1750.o
 obj-$(CONFIG_CM32181)		+= cm32181.o
 obj-$(CONFIG_CM3232)		+= cm3232.o