mali: pick the right GPU voltage table for 1400MHz devices, restore
thresholds

8-level table was always used, resulting in increased voltages for
1400MHz devices. Now, the right table (5-level) can be picked at
runtime.

Restore the thresholds to stock value for more stable frequencies.

Change-Id: I29900535c15557e75c72793b7169771982fce7f9