[ARM] Emit local aliases (.Lfoo$local) for functions

ARMAsmPrinter::emitFunctionEntryLabel() was not calling the base class
function so the $local alias was not being emitted. This should not have
any function effect right now since ARM does not generate different code
for the $local symbols, but it could be improved in the future.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D131392