mali/ux500: Add fullspeed interface

Some users reported that their GPU clocked at 199 kHz.
When ape opp50 is required, mali clock will be divided by 2.
Namely, 399 kHz goes to 199 kHz.
Now, added an interface to monitor this.
Say 1 to set opp100, say 0 to set opp50.

Signed-off-by: cocafe <cocafehj@gmail.com>