staging: rtl8192su: add USB VID/PID for HWNUm-300

The Hercules Wireless N USB mini (HWNUm-300) uses the RTL8191S chipset
and seems to work with this driver.

Signed-off-by: Stephane Glondu <steph@glondu.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>