usbip: vhci-hcd: Clean up the code by adding a new macro

Each vhci has 2*VHCI_HC_PORTS ports, in which VHCI_HC_PORTS
ports are HighSpeed (or below), and VHCI_HC_PORTS are SuperSpeed.
This new macro VHCI_PORTS reflects this configuration.

Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>