new values are based on stabilityTester results
when using 930mV for 1.6GHz and 980mV for 1.8GHz, xhpl failed randomly.
So 930/980mV are the critical operation voltage.Then increase 10mV and
run 100 times test, result shows that xhpl (not always) failed 1~2 times.
It seems +10mV is still not enough to ensure dc-dc output voltage always
above operation voltage, that means the design of dc-dc converter is not
good enough that results in large ripple.
The testing script is "github.com/mzhboy/StabilityTester"
The following configuration have been tested.
1.08-1.32-1.48-1.64-1.8 GHz
900-910-920-930-990 *ok, 930 failed 2/100
900-900-910-940-990 *ok, 990 failed 1/100
890-900-910-940-990 *ok, 990 failed 1/100
880-880-910-940-1000 *ok, 940 failed 2/100
880-880-910-950-1000 *ok, 1000 failed 1/100
880-880-910-950-1010 *ok
