staging: rtlwifi: remove unused functions

Functions rtl_rfreg_delay() and rtl_bb_delay() are unused within the
driver. Both functions call rtl_addr_delay(), this function is unused
outside of these call sites.The driver (and kernel) code base is cleaner
if unused functions are removed.

Remove unused functions.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>