SIS USB2VGA Warning fix

drivers/usb/misc/sisusbvga/sisusb_con.c:1436: warning: initialization from incompatible pointer type

Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Jan Engelhardt <jengelh@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>