staging: wlan-ng: Remove unused function declarations

Several functions are declared but are not implemented or used in any
part of the code. Remove such unimplemented function declarations.

Signed-off-by: Deepak R Varma <drv@mailo.com>
Link: https://lore.kernel.org/r/09e2af8d702e33c15ed9f655b0a1190b4e8bec86.1667308828.git.drv@mailo.com


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