[CUDA] Added --[no-]cuda-include-ptx=sm_XX|all option.

Currently we always include PTX into the fatbin along
with the GPU code.It about doubles the size of the GPU binary
we need to carry in the executable. These options allow control
inclusion of PTX into GPU binary.

This patch does not change the defaults, though we may consider
making no-PTX the default in the future.

Differential Revision: https://reviews.llvm.org/D45495

llvm-svn: 329737