siit: fix kernel 5.16 compile

siit: fix kernel 5.16 compile

siit-1.2/siit.c:1379:9: error: implicit declaration of function
'random_ether_addr' [-Werror=implicit-function-declaration]
 1379 |         random_ether_addr(dev->dev_addr);
      |         ^~~~~~~~~~~~~~~~~

Linux 3.6 renamed random_ether_addr to eth_random_addr [0]
Linux 5.16 removed random_ether_addr [1]

[0]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0a4dd594982a321699000218715e28664ec49169
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ba530fea8ca1b57ee71d4e62f287a5d7ed92f789

Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>