wl18xx: add number of antennas and dc2dc type as module params

We need to specify the number of 2.4GHz and 5GHz antennas and whether
the board has an internal or external DC2DC.  Add some module
parameters that allow changing that.

In the future this will come from the "NVS" file.

Signed-off-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>