modesetting: Remove few common functions from ms namespace

A lot of that code is the same as in xf86-amdgpu and xf86-nouveau drivers. By removing that functions from
ms namespace we can move that code to common implementation.

Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
(cherry picked from commit 5be3b80b)
3 jobs for xserver_1.20/sync_to_slave_outputs in 5 minutes and 8 seconds (queued for 1 second)