Fix update_llc_test_checks.py ARM parsing

When I tried running the script, the ARM regex parser could not parse
my code. It failed because the .Lfunc_end line has a comment at the
end of it, so this commit removes the newline at the end of the regex.

Patch by Joel Galenson!

Differential Revision: https://reviews.llvm.org/D35641

llvm-svn: 309457