drm/panfrost: Fix module unload

When unloading the call to pm_runtime_put_sync_suspend() will attempt to
turn the GPU cores off, however panfrost_device_fini() will have turned
the clocks off. This leads to the hardware locking up.

Instead don't call pm_runtime_put_sync_suspend() and instead simply mark
the device as suspended using pm_runtime_set_suspended(). And also
include this on the error path in panfrost_probe().

Fixes: aebe8c22 ("drm/panfrost: Fix possible suspend in panfrost_remove")
Signed-off-by: Steven Price <steven.price@arm.com>