IB/core: Replace memset with eth_zero_addr

Use eth_zero_addr to assign the zero address to the given address
array instead of memset when second argument is address of zero.

The Coccinelle semantic patch used to make this change is as follows:

// <smpl>
@eth_zero_addr@
expression e;
@@

-memset(e,0x00,ETH_ALEN);
+eth_zero_addr(e);
// </smpl>

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>