Simplify users of StringRef::{l,r}trim (NFC)

r260925 introduced a version of the *trim methods which is preferable
when trimming a single kind of character. Update all users in llvm.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260926 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed