drm/panthor: Evict groups before VM termination

drm/panthor: Evict groups before VM termination

Ensure all related groups are evicted and suspended before VM
destruction takes place.

This fixes an issue where panthor_vm_destroy() destroys and unmaps the
heap context while there are still on slot groups using this.
The FW will do a write out to the heap context when a CSG (group) is
suspended, so a premature unmap of the heap context will cause a
GPU page fault.
This page fault is quite harmless, and do not affect the continued
operation of the GPU.

Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Ketil Johnsen <ketil.johnsen@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251219093546.1227697-1-ketil.johnsen@arm.com
Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>