bus: sunxi-rsb: Fix the return value of sunxi_rsb_device_create()

This code is really spurious.
It always returns an ERR_PTR, even when err is known to be 0 and calls
put_device() after a successful device_register() call.

It is likely that the return statement in the normal path is missing.
Add 'return rdev;' to fix it.

Fixes: d787dcdb

 ("bus: sunxi-rsb: Add driver for Allwinner Reduced Serial Bus")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Tested-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/ef2b9576350bba4c8e05e669e9535e9e2a415763.1650551719.git.christophe.jaillet@wanadoo.fr