staging: rtl8712: remove function get_list_head

get_list_head is an inline that returns &list->head.  This patch removes this
inline and directly applies &list->head where applicable.

Signed-off-by: James A Shackleford <shack@linux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>