libm:also use optimized sqrt/sqrtf on ARM NEON

Summary: Depends on D270 and stacks on top. Fixed from initial patch that was reverted

Test Plan: verified

Reviewers: randall.rushing, jriordan001

Differential Revision: http://review.codefirex.com/D271

Change-Id: I3909d74c67a24f0f6decdeebe7660c9d7e0c558a