[PowerPC] Do not emit HW loop when TLS var accessed in PHI of loop exit

If any PHI nodes in loop exit blocks have incoming values from the
loop that are accesses of TLS variables with local dynamic or general
dynamic TLS model, the address will be computed inside the loop. Since
this includes a call to __tls_get_addr, this will in turn cause the
CTR loops verifier to complain.
Disable CTR loops in such cases.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=48527