Add standard method for enabling mfpu and mcpu code optimization

Conflicts:
	core/combo/arch/arm/armv7-a-neon.mk
build: move bionic optimizations to NEON makefile

Change-Id: Idd495ddbb49f67fef5496456803263f8a23643c5
build: Relax Cortex CFLAGS

 * Always set march=armv7-a
 * Use mtune instead of mcpu. Bad code is generated on A15 otherwise.

Change-Id: Idf8ced8eb0e9d3d4676ca8ec69bf56aed5533bf4
build: Cleanup CPU-specific optimizations

 * TARGET_ARCH_CPU_VARIANT was a Linaro thing. Now that Android
   introducted TARGET_CPU_VARIANT, we should use this instead.
 * Added CFLAGS for Krait and Scorpion after the cleanup.

Change-Id: Iafb40ecefa353a1169c22601be4ce80069c3f587

Conflicts:
	core/combo/arch/arm/armv7-a-neon.mk
	core/combo/arch/arm/armv7-a.mk
add cortex-a5 cpu variant

Change-Id: I369e499d537888eb0f07d900cb50d1424632820e
Specify -mcpu=cortex-a15 for krait CPU variants.

Bug: 11178216

Change-Id: I9922e4cd5ba27e3857798aae5c84299e26e054ea