[PowerPC] support powerpc64le as syntax-checking target (pass2)

Register the Asm Printer for the ppc64le target.

This fills in a spot that was missed in an earlier change (r187179).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202861 91177308-0d34-0410-b5e6-96231b3b80d8