wusb: do a proper channel stop

When stopping the WUSB channel the host should send Channel Stop IEs giving
the WUSB Channel Time of the last MMC.  Both WHCI and HWA hosts provide a
channel stop command for this.

Signed-off-by: David Vrabel <david.vrabel@csr.com>

drivers/usb/host/whci/whci-hc.h

@@ -410,6 +410,8 @@ struct dn_buf_entry {
 #  define WUSBDNTSCTRL_SLOTS(s)    ((s) << 0)
 
 #define WUSBTIME             0x68
+#  define WUSBTIME_CHANNEL_TIME_MASK 0x00ffffff
+
 #define WUSBBPST             0x6c
 #define WUSBDIBUPDATED       0x70