net: ibm: emac: use devm for of_iomap

Allows removing manual iounmap.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20240912024903.6201-4-rosenp@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>