Disable only needed CRTC, read below for more information

Since the begining we have been doing it wrong to get kscreen working
ASAP, we were disabling all outputs that were being updated, which at the
long run created more problems than it solved.

This commit reverts the hacks needed to make the hack work (LOL) and
makes the code work as follow:

-Disable all outputs that need disabling (not used)
-Update all outputs that need update (mode/rotation/pos changed)
-Disable all outputs that previous RECT doesn't fit the new screen one
for example if a output was extended to the right and now is not, the
X will be at XXXX while the new screenSize is YYY
-Enable all outputs that need to be enabled (they were not used before)