Revert "Fix another temp_var_type issue"

This reverts commit 4bc2a79e.

sumpy/tools.py

@@ -299,7 +299,7 @@ class KernelComputation(object):
                 lp.Assignment(id=None,
                     assignee="knl_%d_scaling" % i,
                     expression=sympy_conv(kernel.get_global_scaling_const()),
-                    temp_var_type=lp.Optional(dtype))
+                    temp_var_type=dtype)
                 for i, (kernel, dtype) in enumerate(
                     zip(self.kernels, self.value_dtypes))]