usb serial: support Alcor Micro Corp. USB 2.0 TO RS-232 through pl2303 driver

Patch to add support for Alcor Micro Corp. USB 2.0 TO RS-232 converter.
This patch adds VID and PID to pl2303.[ch], adds it to the "HORRIBLE
HACK FOR PL2303" in usb-serial.c and also prevents cdc-acm to claim
driving this device by blacklisting it in hid-core.

Signed-off-by: Johannes Steingraeber <Jo_Stein@web.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/pl2303.h

@@ -89,3 +89,7 @@
 /* Belkin "F5U257" Serial Adapter */
 #define BELKIN_VENDOR_ID	0x050d
 #define BELKIN_PRODUCT_ID	0x0257
+
+/* Alcor Micro Corp. USB 2.0 TO RS-232 */
+#define ALCOR_VENDOR_ID		0x058F
+#define ALCOR_PRODUCT_ID	0x9720