[OpenMP][FIX] Emit debug declares only if debug info is available

The `EmitDeclareOfAutoVariable` introduced in D114504 and D115510 has a
precondition that cannot be violated. It is unclear if we should call it
directly given the sparse usage in clang but for now we should at least
not crash if the debug info kind is too low.

Fixes #52938.

Differential Revision: https://reviews.llvm.org/D116865