staging: rtl8712: Add device ID for Sitecom WLA2100

commit 1e6e6328

 upstream.

This adds the USB ID for the Sitecom WLA2100. The Windows 10 inf file
was checked to verify that the addition is correct.

Reported-by: Frans van de Wiel <fvdw@fvdw.eu>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Frans van de Wiel <fvdw@fvdw.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zefan Li <lizefan@huawei.com>