[Driver] Remove confusing *-linux-android detection with non-android --target=

These values allow, for example, `--target=aarch64` and
`--target=aarch64-linux-gnu` to detect `aarch64-linux-android`. This is
confusing. Users should specify `--target=aarch64-linux-android` to get Android GCC
installation.

Reverts D53463.

Reviewed By: nickdesaulniers, danalbert

Differential Revision: https://reviews.llvm.org/D110379