[flang] Don't complain about implicitly-typed dummy arguments inherited into...

[flang] Don't complain about implicitly-typed dummy arguments inherited into an IMPLICIT NONE submodule

When a module procedure's interface is defined in an ancestor (sub)module
with an implicitly typed dummy argument, don't emit a bogus error in
the separate module procedure later if its submodule has IMPLICIT NONE.

Fixes llvm-test-suite/Fortran/gfortran/regression/submodule_26.f90.

Differential Revision: https://reviews.llvm.org/D157335