Nio supports switching between 60 and 90 Hz refresh rates, pstar between
48, 60, 90, 120 and 144 Hz, so let's expose it in
Settings -> Display -> Peak refresh rate for users to save battery
if necessary.
Smooth display only changes between 48 and 144 Hz, which can cause
flickering on certain brightness levels, so let the user chose
which range he prefers.
Test: visual confirmation after toggling several times
Change-Id: Ia206c495e3f40f583f8cd35e7753c30a5e917656
3f2fa585cb