cxgb4: fix coccinelle warnings

Commit 16e47624

 ("cxgb4: Add new scheme to update T4/T5 firmware")
introduced below coccinelle warning.

>> drivers/net/ethernet/chelsio/cxgb4/t4_hw.c:994:2-8: Replace memcpy with
   struct assignment

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>