wifi: cfg80211: move away from using a fake platform device

Downloading regulatory "firmware" needs a device to hang off of, and so
a platform device seemed like the simplest way to do this.  Now that we
have a faux device interface, use that instead as this "regulatory
device" is not anything resembling a platform device at all.

Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: <linux-wireless@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/2025070116-growing-skeptic-494c@gregkh


Signed-off-by: Johannes Berg <johannes.berg@intel.com>