qlnxe: Remove a pointless copy back from the link-layer address

On ifnet attaching, ether_ifattach() makes the link-layer address by
shadow copying the ha->primary_mac. Well, the link-layer address will
not be altered during attaching, thus it is pointless to copy it back.

No functional change intended.

Reviewed by: kbowling
MFC after: 5 days
Differential Revision: https://reviews.freebsd.org/D54883