drivers: net: cpsw-common: Fix reading of mac address for am43 SoCs

cpsw driver tries to get macid for am43xx SoCs using the compatible
ti,am4372. But not all variants of am43x uses this complatible like
epos evm uses ti,am438x. So use a generic compatible ti,am43 to get
macid for all am43 based platforms.

Reviewed-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>