staging: usbip: cleanup and fix of vhci_hub_status

Changed setting the status bits to a byte-oriented approach. Number of
written status bits is now based on VHCI_NPORT, instead of casting
status buffer to a long. This fixes a stack corruption bug on 64-bit
based architectures, and potential byte order / endianness related
issues.

In addition updated function comments, and log statements.

Signed-off-by: Bart Westgeest <bart@elbrys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>