Revert "arm64: Use builtin for nearbyintf/nearbyint"

This reverts commit 35d8ba30.

Reason for revert: caused test failures...

[  FAILED  ] math_h_force_long_double.nearbyint (15 ms)
bionic/tests/math_test.cpp:(1080) Failure in test math_h_force_long_double.nearbyint
Value of: (fetestexcept(FE_ALL_EXCEPT) & FE_INEXACT) == 0
  Actual: false
Expected: true
math_h_force_long_double.nearbyint exited with exitcode 1.

Change-Id: If8e3a3dfbd0e7ee071e5187f96749b6acbb5fc05