linux-imx

driver: regulator: pf8x00-regulator: Fix voltage set time

The voltage set time has been caclulated wrong as the wrong index
of the ramp_rate table has been selected. Also the abs() value
of the voltage diff has to be used. As this is a unsigned value.

Also updated variable names and added comments to make it more readable.

Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
Signed-off-by: Christian Hemp <c.hemp@phytec.de>