Do not lower VSETCC if operand is an f16 vector

Summary:
SETCC with f16 vectors has OperationAction set to Expand but still gets
lowered to FCM* intrinsics based on its result type.  This patch skips
lowering of VSETCC if the operand is an f16 vector.

v4 and v8 tests included.

Reviewers: ab, jmolloy

Subscribers: srhines, llvm-commits

Differential Revision: http://reviews.llvm.org/D15361

llvm-svn: 258471