drm/radeon/atom: fix fb when fetching engine params

For correctness.  The fb divider isn't actually used
in any of the relevant dpm code.  It's calculated
from the other parameters.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --cc drivers/gpu/drm/radeon/radeon_atombios.c
Simple merge