[BreakFalseDeps] ignore function with minsize attribute

This came up in the x86-specific:
https://bugs.llvm.org/show_bug.cgi?id=43239
...but it is a general problem for the BreakFalseDeps pass.
Dependencies may be broken by adding some other instruction,
so that should be avoided if the overall goal is to minimize size.

Differential Revision: https://reviews.llvm.org/D67363

llvm-svn: 372628