Remove unneeded intrinsics from Blackfin backend.

__builtin_bfin_ones does the same as ctpop, so it can be implemented in the front-end.

__builtin_bfin_loadbytes loads from an unaligned pointer with the disalignexcpt instruction. It does the same as loading from a pointer with the low bits masked. It is better if the front-end creates a masked load. We can always instruction select the masked to disalignexcpt+load.

We keep csync/ssync/idle. These intrinsics represent instructions that need workarounds for some silicon revisions. We may even want to convert inline assembler to intrinsics to enable the workarounds.

llvm-svn: 77917