drm/qxl: switch to using drm_exec v2

Just a straightforward conversion without any optimization.

Only compile tested for now.

v2: rebase

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241114153020.6209-3-christian.koenig@amd.com