panfrost: avoid potential divide by 0 calculating timer_resolution

On armhf integer divide by 0 can raise SIGFPE, whereas on aarch64
it just returns 0. This has become an issue because the recently
added panfrost_init_screen_caps always calls pan_gpu_time_to_ns to
calculate caps->timer_resolution, whereas before we only called it
when PIPE_CAP_TIMER_RESOLUTION was queried, and only OpenCL
does that (and not always).

Fixes: 205669e3a9 ("panfrost: add panfrost_init_screen_caps")
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33435>

src/gallium/drivers/panfrost/pan_device.h

@@ -229,6 +229,7 @@ pan_is_bifrost(const struct panfrost_device *dev)
 static inline uint64_t
 pan_gpu_time_to_ns(struct panfrost_device *dev, uint64_t gpu_time)
 {
+   assert(dev->kmod.props.timestamp_frequency > 0);
    return (gpu_time * NSEC_PER_SEC) / dev->kmod.props.timestamp_frequency;
 }
 

src/gallium/drivers/panfrost/pan_screen.c

@@ -576,7 +576,8 @@ panfrost_init_screen_caps(struct panfrost_screen *screen)
       dev->kmod.props.gpu_can_query_timestamp &&
       dev->kmod.props.timestamp_frequency != 0;
 
-   caps->timer_resolution = pan_gpu_time_to_ns(dev, 1);
+   if (caps->query_timestamp)
+      caps->timer_resolution = pan_gpu_time_to_ns(dev, 1);
 
    /* The hardware requires element alignment for data conversion to work
     * as expected. If data conversion is not required, this restriction is