wl1271: added missing packed modifier in some cmd structs

Some of the struct definitions in the wl1271_acx.h file were missing the
__attribute__ ((packed)) modifier.

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>