fortran: Reuse associated_dummy memory if previously allocated [PR108923]
This avoids making the associted_dummy field point to a new memory chunk
if it's already pointing somewhere, in which case doing so would leak the
previously allocated chunk.
PR fortran/108923
gcc/fortran/ChangeLog:
* intrinsic.cc (get_intrinsic_dummy_arg,
set_intrinsic_dummy_arg): Rename the former to the latter.
Remove the return value, add a reference to the lhs as argument,
and do the pointer assignment inside the function. Don't do
it if the pointer is already non-NULL.
(sort_actual): Update caller.