dt-bindings:iio:light:sharp,gp2ap020a00f: txt to yaml conversion.

Simple conversion.
Jacek's email bounced, by Kyungmin's still seems good so just dropped
Jacek from maintainer list.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Link: https://lore.kernel.org/r/20201031184854.745828-17-jic23@kernel.org