Fortran: Fix type-decl for PDT / wrong-code pdt_14.f03 issue [PR97652]

Parameterized derived types are handled in a special way and start with 'Pdt'.
If the 'P' is not uppercase, gfc_get_derived_type (which calls
gfc_get_module_backend_decl) does not find the existing declaration and
builds a new type. The middle end then sees those types as being different
and nonalising, creating an endless loop for pdt_14.f03.

gcc/fortran/ChangeLog:

	PR fortran/97652
	* module.c (mio_symbol): Fix symbol name for pdt_type.