Revert "drm/radeon/kms: switch back to min->max pll post divider iteration"

This reverts commit a6f97617.

Remove this commit as it is no longer necessary. The relevant bugs
were fixed properly in:
drm/radeon/kms: hopefully fix pll issues for real (v3)
5b40ddf8
drm/radeon/kms: add missing frac fb div flag for dce4+
9f4283f4

This commit also broke certain ~5 Mhz modes on old arcade monitors,
so reverting this commit fixes:
https://bugzilla.kernel.org/show_bug.cgi?id=29502



Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>