Documentation: bindings: Add missing Amlogic SCPI sensor bindings

amlogic,meson-gxbb-scpi-sensors is both the driver and DT but is not
documented. Just add it to amlogic's scpi documentation

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>