selftests/hid: fix ruff linter complains

rename ambiguous variables l, r, and m, and ignore the return values
of uhdev.get_evdev() and uhdev.get_slot()

Acked-by: Jiri Kosina <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Benjamin Tissoires <[e-mail]>

tools/testing/selftests/hid/tests/test_mouse.py

···
         :param reportID: the numeric report ID for this report, if needed
         """
         if buttons is not None:
-            l, r, m = buttons
-            if l is not None:
-                self.left = l
-            if r is not None:
-                self.right = r
-            if m is not None:
-                self.middle = m
+            left, right, middle = buttons
+            if left is not None:
+                self.left = left
+            if right is not None:
+                self.right = right
+            if middle is not None:
+                self.middle = middle
         left = self.left
         right = self.right
         middle = self.middle

tools/testing/selftests/hid/tests/test_wacom_generic.py

···
         Ensure that the confidence bit being set to false should not result in a touch event.
         """
         uhdev = self.uhdev
-        evdev = uhdev.get_evdev()
+        _evdev = uhdev.get_evdev()
 
         t0 = test_multitouch.Touch(1, 50, 100)
         t0.confidence = False
···
         events = uhdev.next_sync_events()
         self.debug_reports(r, uhdev, events)
 
-        slot = self.get_slot(uhdev, t0, 0)
+        _slot = self.get_slot(uhdev, t0, 0)
 
         assert not events