drm/panthor: validate userspace queue count against initialized firmware slot count

In the Linux kernel, the following vulnerability has been resolved:

drm/panthor: validate userspace queue count against initialized firmware slot count

In panthor_drv.c:panthor_ioctl_group_create(),
the queue count is validated against the hardcoded maximum:

if (!args->queues.count || args->queues.count > MAX_CS_PER_CSG)
return -EINVAL;

However, if the firmware reports fewer slots than MAX_CS_PER_CSG,
panthor_fw_init_ifaces() will only initialize that smaller number of
stream interfaces.

If unprivileged userspace requests more queues than the firmware reported
(but no more than MAX_CS_PER_CSG), cs_slot_prog_locked() fetches an
uninitialized stream interface and may crash when dereferencing
cs_iface->input->ringbuf_base.