Maximum voltage is 21 V

With PD 3.0, the highest voltage is 21 V (available on 20V Prog APDOs).
The firmware now allows that voltage to be configured.

lib/include/pd.h

@@ -339,7 +339,7 @@
  * Unit constants
  */
 #define PD_MV_MIN 0
-#define PD_MV_MAX 20000
+#define PD_MV_MAX 21000
 #define PD_PDV_MIN PD_MV2PDV(PD_MV_MIN)
 #define PD_PDV_MAX PD_MV2PDV(PD_MV_MAX)
 #define PD_MA_MIN 0