libertas: Add missing __packed annotation with struct_group()

Build testing of the newly added struct_group() usage missed smaller
architecture width tests for changes to pahole output. Add the missed
__packed annotation with struct_group() usage in a __packed struct.
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/linux-mm/202111302102.apaePz2J-lkp@intel.com
Fixes: 5fd32ae0 ("libertas: Use struct_group() for memcpy() region")
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211201173234.578124-2-keescook@chromium.org

drivers/net/wireless/marvell/libertas/host.h

@@ -308,7 +308,7 @@ struct txpd {
 	__le32 tx_packet_location;
 	/* Tx packet length */
 	__le16 tx_packet_length;
-	struct_group(tx_dest_addr,
+	struct_group_attr(tx_dest_addr, __packed,
 		/* First 2 byte of destination MAC address */
 		u8 tx_dest_addr_high[2];
 		/* Last 4 byte of destination MAC address */