net: axinet: Use of_property_read_u32 instead of open-coding it

Use of_property_read_u32 instead of of_get_property with return value
checks and endianness conversion.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Reviewed-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>