USB: fix sign-extension bug in the hub driver

This patch (as1646) fixes a long-standing bug in the USB hub driver.
Upon conversion from char to unsigned long, the bytes in the status
buffer are subject to unwanted sign extension.  The bytes should be
declared as u8 rather than char, to prevent this.

This effects of this bug are minimal.  The hub driver may end up doing
a little unnecessary extra work because it thinks events have occurred
on some ports when they really haven't.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>