net: qcom/emac: fix a sizeof() typo

We had intended to say "sizeof(u32)" but the "u" is missing.
Fortunately, sizeof(32) is also 4, so the original code still works.

Fixes: c4e7beea

 ("net: qcom/emac: add ethtool support for reading hardware registers")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>