usb: host: xhci: print HCIVERSION on debug

When calling xhci_dbg_regs() we actually _do_ want to know XHCI's
version. This might help figure out why certain problems only happen
in some cases.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>