[NVPTX] Fixed vectorized LDG for f16.

v2f16 is a special case in NVPTX. v4f16 may be loaded as a pair of v2f16
and that was not previously handled correctly by tryLDGLDU()

Differential Revision: https://reviews.llvm.org/D45339

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@329456 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed