Make gemmlowp properly support host modules.

  - ANDROID is set on all compiles in the android tree;
    __ANDROID__ is set when targeting an android device
  - gemmlowp should only be checking __ANDROID__ when including
    android/api-level.h
  - Also removes obsolete / duplicated files.

Test: mm
Test: nnapi_example tests all pass
Change-Id: I4f52860ed36b01194c66c5fb7622721407656fc0
9 files changed