v2: move declarations into libdrm
v3: fix typos
    rework handling of how much memory to reserve
v4: remove unused parameter
    unmap cutout on error and when the screen is destroyed
v5: move into screen_create
    enable HMM only if CL gets enabled

Signed-off-by: Karol Herbst <kherbst@redhat.com>
Part-of: <mesa/mesa!5906>