Added tSinkRequest to pd.h

src/pd.h

 #define PD_T_HARD_RESET_COMPLETE MS2ST(4)
 #define PD_T_PS_TRANSITION MS2ST(500)
 #define PD_T_SENDER_RESPONSE MS2ST(27)
+#define PD_T_SINK_REQUEST MS2ST(100)
 #define PD_T_TYPEC_SINK_WAIT_CAP MS2ST(465)
-/* This is actually a Type-C time value, not a Power Delivery time value, but
- * who cares? */
+/* This is actually from Type-C, not Power Delivery, but who cares? */
 #define PD_T_PD_DEBOUNCE MS2ST(15)