usb: misc: sisusbvga: fix information leak to userland

Structure sisusb_info is copied to userland with "sisusb_reserved" field
uninitialized.  It leads to leaking of contents of kernel stack memory.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>