Revert "[ARM NEON] libm: original optimized modf"

This reverts commit fab68555c7199dbefb055f5da844287bab5efdcc.

Change-Id: I1f69fb87b3cac303bc30ce0a0e31f6480b1b94e9
Merge branch 'kitkat' of https://github.com/AICP/bionic into HEAD