wl1271: remove deprecated ACX definition

As of Rev. 6.1.0.0.335, the ACX_SET_SMART_REFLEX_DEBUG command is
deprecated.  This patch removes it from the wl1271 driver (it wasn't used
anyway).

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Reviewed-by: Saravanan Dhanabal <ext-saravanan.dhanabal@nokia.com>