wlcore/wl12xx: move ref_clock and tcxo_clock elements to wl12xx

Only wl12xx needs to get the ref_clock anc tcxo_clock values from the
platform data.  Move these elements from the wl1271 structure to
wl12xx's private data.

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