Accurately set DPM minimum current

I took an accurate reading of the current consumed by the PD Buddy Sink
in various states, and found that the lowest current I could safely set
as the amount it requests when the output is turned off was 30 mA.
I therefore changed it to request this lower current to avoid asking for
more than we need.

(cherry picked from commit 88766783de)

src/device_policy_manager.c

@@ -29,7 +29,7 @@
 
 
 /* The current draw when the output is disabled */
-#define DPM_MIN_CURRENT PD_MA2PDI(100)
+#define DPM_MIN_CURRENT PD_MA2PDI(30)
 
 
 /*