drm/panthor: validate group queue count

A panthor group can have at most MAX_CS_PER_CSG panthor queues.

Fixes: 4bdca115 ("drm/panthor: Add the driver frontend block")
Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> # v1
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20250903192133.288477-1-olvaffe@gmail.com