ksz884x: Use kzalloc rather than kmalloc followed by memset with 0

This considers some simple cases that are common and easy to validate
Note in particular that there are no ...s in the rule, so all of the
matched code has to be contiguous

The semantic patch that makes this change is available
in scripts/coccinelle/api/alloc/kzalloc-simple.cocci.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: David S. Miller <davem@davemloft.net>