qxl fb rendering and reservations fixes

[Dave Airlie]

Okay these are a bit large but I'd like to put them into -fixes ASAP,
as qxl totally fails on -rc1/2 due to the lockdep and reservation warnings,

The first patch is just a fix for broken rendering while rendering from
an irq context, it also fixes sleep while atomic issues.

The second patch is just prepartory for the reservation rework, which
is the 3rd and largest patch.

Dave.