Add support for Apple Silicon (M1, M2, M3, …)

[blazer82]

Add support for Apple GPUs

• Use --use_mps to enable Apple Silicon GPU support

e.g.

python demo.py --task FaceEnhancement --model GPEN-BFR-512 --in_size 512 --channel_multiplier 2 --narrow 1 --use_sr --sr_scale 4 --use_mps --indir examples/imgs --outdir examples/outs-bfr