power: rk808: fix ldo register offset

power: rk808: fix ldo register offset

Till now get_ldo_reg did a return &rk808_ldo[num - 1]; to return
the ldo register offset but didn't take into account that its
calling functions already created the ldo as ldo = dev->driver_data - 1.

This resulted in the setting for ldo8 writing to the register of ldo7
and so on. So fix this and get the correct ldo register data.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Simon Glass <sjg@chromium.org>