Fix wrong usages of CTR/MCTR where CTR8/MCTR8 was meant.

Fix wrong usages of CTR/MCTR where CTR8/MCTR8 was meant.

- Check for MTCTR8 in addition to MTCTR when looking up a hazard.

- When lowering an indirect call use CTR8 when targeting 64bit.

- Introduce BCTR8 that uses CTR8 and use it on 64bit when expanding ISD::BRIND.

The last change fixes PR8487. With those changes, we are able to compile a
running "ls" and "sh" on FreeBSD/PowerPC64.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132552 91177308-0d34-0410-b5e6-96231b3b80d8