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.

llvm-svn: 132552