net: ti: am65-cpsw-nuss: Use approved property to get efuse address

The approved DT property for MAC efuse (ROM) address is
"ti,syscon-efuse".

Use that and drop custom property "mac_efuse".

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Acked-by: Nishanth Menon <nm@ti.com>