edtlib: re-appease the linter

At some point in the past, we had to suppress a couple of false
positive pylint warnings to pass CI. But now the linter seems to have
figured out its original mistake and is complaining about a useless
supression. Sigh. Play along.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

scripts/dts/python-devicetree/src/devicetree/edtlib.py

@@ -818,9 +818,7 @@ def flash_controller(self):
     def spi_cs_gpio(self):
         "See the class docstring"
 
-        # We know on_buses is always a list, but pylint doesn't.
-        # So ignore the error.
-        if not ("spi" in self.on_buses # pylint: disable=unsupported-membership-test
+        if not ("spi" in self.on_buses
                 and "cs-gpios" in self.bus_node.props):
             return None
 
@@ -873,9 +871,7 @@ def _init_binding(self):
                 # works the same way in Zephyr as it does elsewhere.
                 binding = None
 
-                # We know on_buses is always a list, but pylint doesn't.
-                # So ignore the error.
-                for bus in on_buses: # pylint: disable=not-an-iterable
+                for bus in on_buses:
                     if (compat, bus) in self.edt._compat2binding:
                         binding = self.edt._compat2binding[compat, bus]
                         break