wl12xx: use the conf struct instead of macros for memory configuration

make the configuration management more flexible by using the
conf struct, rather than predefined macros.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Reviewed-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>