mfd: syscon: Return -EPROBE_DEFER if the syscon is not found

These days we can register syscons with of_syscon_register_regmap() so
when we can't find the syscon that probably means it hasn't been
registered yet. Return -EPROBE_DEFER so the driver will try probing
again.

Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Arnd Bergmann <[e-mail]>
Reviewed-by: Chen-Yu Tsai <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/syscon.c

···
 		if (create_regmap)
 			syscon = of_syscon_register(np, check_res);
 		else
-			syscon = ERR_PTR(-EINVAL);
+			syscon = ERR_PTR(-EPROBE_DEFER);
 	}
 	mutex_unlock(&syscon_list_lock);