staging: rtl8723bs: remove unused struct rtw_regulatory

staging: rtl8723bs: remove unused struct rtw_regulatory

The struct rtw_regulatory is never used in the rtl8723bs driver.
Functions taking it as a parameter are always passed NULL and
perform no logic with it. Remove the dead code and the struct.

Suggested-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Kenet Jovan Sokoli <deep@crimson.net.eu.org>
Reviewed-by: Dan Carpenter <error27@gmail.com>
Link: https://patch.msgid.link/20260414081325.142313-1-deep@crimson.net.eu.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>