Revert "frameworks/rs: workaround with newer clang's"

This was sloppy as fuck and it doesn't even address the issue.

This reverts commit de6d5679c9236de7c0c46f445ca92aedcf0ede23.

Change-Id: Ia157a0a5cdc8734bcb1ac239271802ac11c2f037
C++11: turn off error warning for only the error we want to turn off

previously was setting -Wno-error to get arround C++11 narrowing violations

Change-Id: I620b1d524bce4642f3f0b4af446e00394177e42b
CLANG: Workaround for violations on unsupported command -mtune=cortex-a15

Clang doesn't support -mtune=cortex-a15 and newer ones will error out if this
is assigned.

Change-Id: Idf3b8850314717f99d0cdda65490f5af5c336fc8