Revert removal of F16 literal support for non ARM/SPIR Targets

This reverts commit 57a6ce7a and 248e5bf6.

frameworks/ml/nn still makes heavy use of _Float16 on x86. Let's keep
this working until they figure out a way to avoid using it.

Bug: 127391056
Change-Id: I98192c407ec1192ec6e340646ffc2c3d86f83d3b
4 files changed