IR: Allow 32-bits for lines in debug location

IR: Allow 32-bits for lines in debug location

Remove unnecessary restriction of 24-bits for line numbers in
`MDLocation`.

The rest of the debug info schema (with the exception of local
variables) uses 32-bits for line numbers.  As I introduce the
specialized nodes, it makes sense to canonicalize on one size or the
other.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228455 91177308-0d34-0410-b5e6-96231b3b80d8