staging: r8188eu: convert rtw_p2p_get_groupid to return void

rtw_p2p_get_groupid always returns 0 and it's return value is not used.
Convert it to return void.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Abdun Nihaal <abdun.nihaal@gmail.com>
Link: https://lore.kernel.org/r/be08b2d84a7fc836db5aa008d906dee1b282fa54.1643466748.git.abdun.nihaal@gmail.com


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