Makefile: cleanup compiler flags for neon-vfpv4

Also test cortex-a8 might be closer mcpu target for krait via @Morfic
https://bitbucket.org/morfic/trinity_five/commits/beb5c4d358c76e932fc3e2c8747dfebb60c08aac

This may be legit..Initial testing shows improvement in 0xbench VM, Linpack and Antutu CPU
tests.

Plus add various flags from @Sabermod and use neon-vfpv4 instead of neon

Change-Id: Ia9ff464effb38a16723af25285fb37bb2c1d3fc4
Signed-off-by: Rob Beane <robbeane@gmail.com>