[autotest] Enable firmware install for servo v4.

CQ-DEPEND=CL:352820
CQ-DEPEND=CL:383591
BUG=chromium:643081
TEST=not yet

Change-Id: I8df2c8961031041fee2c06affc8f5a0a794d64a6
Reviewed-on: https://chromium-review.googlesource.com/383592
Commit-Ready: Wai-Hong Tam <waihong@google.com>
Tested-by: Wai-Hong Tam <waihong@google.com>
Reviewed-by: Wai-Hong Tam <waihong@google.com>
diff --git a/server/cros/servo/servo.py b/server/cros/servo/servo.py
index fd91a95..01f92f9 100644
--- a/server/cros/servo/servo.py
+++ b/server/cros/servo/servo.py
@@ -695,7 +695,10 @@
         if servo_version.startswith('servo_v2'):
             self._programmer = firmware_programmer.ProgrammerV2(self)
             self._programmer_rw = firmware_programmer.ProgrammerV2RwOnly(self)
-        elif servo_version.startswith('servo_v3'):
+        # Both servo v3 and v4 use the same programming methods so just leverage
+        # ProgrammerV3 for servo v4 as well.
+        elif (servo_version.startswith('servo_v3') or
+              servo_version.startswith('servo_v4')):
             self._programmer = firmware_programmer.ProgrammerV3(self)
             self._programmer_rw = firmware_programmer.ProgrammerV3RwOnly(self)
         else: