staging: prima: Allow prima_wlan to be built inside kernel

* Prima needs wcnss to be set up when it loads.
  Therefore use a platform_driver in to notify prima that wcnss is ready.

Conflicts:
    drivers/staging/prima/CORE/HDD/src/wlan_hdd_main.c

Change-Id: I6c403f705e9dffa524a2aab54453e50775b45264