cpufreq: remove old undervolting settings
drivers: cpufreq: add voltage settings

this change will enable under|over voltage
settings by sysfs (userspace)

at least, the min/max values are:

min: 600mV
max: 1500mv

PS2: fix white spaces and tabs
PS3: fix white space

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: I3355a7e2c9e0119ddb82c3dc8549930986ede1ce