drm/amdkfd: Correct F8_MODE for gfx950

Correct F8_MODE setting for gfx950 that was removed

Fixes: 1a9dbc31

Signed-off-by: Amber Lin <Amber.Lin@amd.com>
Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviwanathan@amd.com>