staging: r8188eu: make validate_recv_mgnt_frame return void

Change the validate_recv_mgnt_frame function to not return a status.

It always returns _SUCCESS, its only caller does not check the
return value.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220403163818.357173-2-martin@kaiser.cx


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