Update src/stdlib_linalg_iterative_solvers_cg.fypp

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Author: jalvesz

src/stdlib_linalg_iterative_solvers_cg.fypp

@@ -75,7 +75,7 @@ contains
         ${t}$, intent(in) :: b(:)
         ${t}$, intent(inout) :: x(:)
         ${t}$, intent(in), optional :: tol
-        logical(1), intent(in), optional, target  :: di(:)
+        logical(int8), intent(in), optional, target  :: di(:)
         integer, intent(in), optional :: maxiter
         logical, intent(in), optional  :: restart
         type(solver_workspace_${s}$_type), optional, intent(inout), target :: workspace