staging: rtl8172: fixed comment style in rts871x_cmd.c

Fixed comment style warning by checkpatch:

* Block comments use * on subsequent lines
* Block comments use a trailing */ on a separate line

Signed-off-by: Louie Lu <louie.lu@hopebaytech.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>