Revert "build: Relax Cortex CFLAGS"

This reverts commit 58dc899c94a4d501a992ad432975285b7c154464

we already have what this does. it also reverts a commit from linaro.
Avoid mtuning an empty TARGET_ARCH_VARIANT_CPU

Change-Id: I385fa7a5bee2734eb95ab92fc3a36589c48bb0ef
Merge remote-tracking branch 'aosp/master' into jb42-master

Change-Id: Iba2ca1d4bce8f33b3e3d4e5f4b8ca8a804cb45a9
Fixes

Change-Id: Id942498ddfe3e3d58919ec797aef1c7404619358
Merge remote-tracking branch 'vanir/jb42-master' into jb42-master

Change-Id: Ia483687a436debdfd293d6562ce32cf0d8ce711e