[CodeGen] Don't omit any redundant information in -debug output

In r322867, we introduced IsStandalone when printing MIR in -debug
output. The default behaviour for that was:

1) If any of MBB, MI, or MO are -debug-printed separately, don't omit any
redundant information.

2) When -debug-printing a MF entirely, don't print any redundant
information.

3) When printing MIR, don't print any redundant information.

I'd like to change 2) to:

2) When -debug-printing a MF entirely, don't omit any redundant information.

Differential Revision: https://reviews.llvm.org/D43337

llvm-svn: 326094