charger configuration and provide some basic control knobs to
set charger voltage and dump config on boot. Two loader tunables
have been added:
o hw.am335x_pmic.bootverbose set to 1 to get more info on the
boot;
o hw.am335x_pmic.vo: set to charger voltage to be applied on
kernel initialization time, supported values are "4.10V",
"4.15V", "4.20V" and "4.25V".
Cleanup code a bit in general, move TPS65217 register
definitions into a separate header, convert bit-banging
defines into bitmap structures.
Also threat the case when power source is neither "AC" nor "USB"
as "Battery", not "Unknown".
