bnxt_en: Fix W=stringop-overflow warning in bnxt_dcb.c

bnxt_en: Fix W=stringop-overflow warning in bnxt_dcb.c

Fix the following warning:

drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c: In function ‘bnxt_hwrm_queue_cos2bw_cfg’:
cc1: error: writing 12 bytes into a region of size 1 [-Werror=stringop-overflow ]
In file included from drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c:19:
drivers/net/ethernet/broadcom/bnxt/bnxt_hsi.h:6045:17: note: destination object ‘unused_0’ of size 1
 6045 |         u8      unused_0;

Fix it by modifying struct hwrm_queue_cos2bw_cfg_input to use an array
of sub struct similar to the previous patch.  This will eliminate the
pointer arithmetc to calculate the destination pointer passed to
memcpy().

Link: https://lore.kernel.org/netdev/CACKFLinikvXmKcxr4kjWO9TPYxTd2cb5agT1j=w9Qyj5-24s5A@mail.gmail.com/
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230807145720.159645-3-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>