drm/amdkfd: NULL dereference involving create_process()

We accidentally return ERR_PTR(0) which is NULL.  The caller is not
expecting that and it leads to an Oops.

Fixes: dd59239a ("amdkfd: init aperture once per process")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

drivers/gpu/drm/amd/amdkfd/kfd_process.c

@@ -318,7 +318,8 @@ static struct kfd_process *create_process(const struct task_struct *thread)
 
 	/* init process apertures*/
 	process->is_32bit_user_mode = in_compat_syscall();
-	if (kfd_init_apertures(process) != 0)
+	err = kfd_init_apertures(process);
+	if (err != 0)
 		goto err_init_apretures;
 
 	return process;