cnss: Vote for the WLAN antenna switch regulator

In some targets, explicitly turning on/off the regulator for WLAN
antenna switch is needed to enable/dsiable antenna sharing capacity.
Hence add the change to achieve this based on device tree option.

Change-Id: Ic04019cbe9c42bc92a65f308f56f307c52346d92
Signed-off-by: Yue Ma <yuem@codeaurora.org>