The constant initialization for globals in NVPTX is generated as an

The constant initialization for globals in NVPTX is generated as an
array of bytes. The generation of this byte arrays was expecting
the host to be little endian, which prevents big endian hosts to be
used in the generation of the PTX code. This patch fixes the
problem by changing the way the bytes are extracted so that it
works for either little and big endian.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239412 91177308-0d34-0410-b5e6-96231b3b80d8