drm/amd/powerplay: Delete unused function and maths library

drm/amd/powerplay: Delete unused function and maths library

We start with the function 'atomctrl_calculate_voltage_evv_on_sclk'
which has been unused since 2016's commit
e805ed83ba1c ("drm/amd/powerplay: delete useless files.")

Remove it.

It was also the last user of the entire fixed point maths library in
ppevvmath.h.

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>