firmware-qcom-adreno: drop the include file

Historically meta-qcom had a special way of providing Adreno firmware
files. With the Adreno firmware for SM8x50 being a part of
linux-firmware this has mostly lost sense and now it has been
transformed into the 'PROPRIETARY_URI' support in the
firmware-qcom-hlos.inc. Since none of the boards in meta-qcom uses
firmware-qcom-adreno.inc anymore, drop it from the layer.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Author: lumag