skpbench: filter out junk spewed by Pixel C driver

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2488043003

Review-Url: https://codereview.chromium.org/2488043003
diff --git a/tools/skpbench/_hardware.py b/tools/skpbench/_hardware.py
index 525c4c1..de8848d 100644
--- a/tools/skpbench/_hardware.py
+++ b/tools/skpbench/_hardware.py
@@ -29,6 +29,10 @@
   def __exit__(self, exception_type, exception_value, traceback):
     pass
 
+  def filter_line(self, line):
+    """Returns False if the provided output line can be suppressed."""
+    return True
+
   def sanity_check(self):
     """Raises a HardwareException if any hardware state is not as expected."""
     pass