MIPS: ath25: Convert random_ether_addr to eth_random_addr

random_ether_addr is a #define for eth_random_addr which is
generally preferred in kernel code by ~3:1

Convert the uses of random_ether_addr to enable removing the #define

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/19600/
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@linux-mips.org