eth: bnxt: fix one of the W=1 warnings about fortified memcpy()

Fix a W=1 warning with gcc 13.1:

In function ‘fortify_memcpy_chk’,
    inlined from ‘bnxt_hwrm_queue_cos2bw_cfg’ at drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c:133:3:
include/linux/fortify-string.h:592:25: warning: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Wattribute-warning]
  592 |                         __read_overflow2_field(q_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The field group is already defined and starts at queue_id:

struct bnxt_cos2bw_cfg {
	u8			pad[3];
	struct_group_attr(cfg, __packed,
		u8		queue_id;
		__le32		min_bw;
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20230727190726.1859515-2-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c

@@ -130,7 +130,7 @@ static int bnxt_hwrm_queue_cos2bw_cfg(struct bnxt *bp, struct ieee_ets *ets,
 					    BW_VALUE_UNIT_PERCENT1_100);
 		}
 		data = &req->unused_0 + qidx * (sizeof(cos2bw) - 4);
-		memcpy(data, &cos2bw.queue_id, sizeof(cos2bw) - 4);
+		memcpy(data, &cos2bw.cfg, sizeof(cos2bw) - 4);
 		if (qidx == 0) {
 			req->queue_id0 = cos2bw.queue_id;
 			req->unused_0 = 0;