exclude src/ports/*CG* for all targets

We were not excluding it from iOS builds, which fails including MobileCoreServices.h.  (Odd!)

Also remove some redudant exclusions of src/ports/SkImageDecoder_CG.cpp, and sorts.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1782903002

Review URL: https://codereview.chromium.org/1782903002