Revert^2 "ARM64: toHalf() intrinsic for ARMv8"

This reverts commit 67bf99b8a575b15c117a3fbf7aae421330e4795a.

Reason for revert: The original CL was reverted because
of build breakages not directly related to the CL itself.

Change-Id: Ic98e9912701d81d73bc3af719a7e3a8e44e8c058
11 files changed