ehci: speed up initialization

According to EHCI specification v1.0, the controller should stabilize
the power on a port at most 20 ms after the port power bit transition.
So, we put this setting in the virtual descriptor corresponding field,
(bPwrOn2PwrGood = 10 => 10 x 2ms = 20ms), this saves about 500ms at each
controller initialization/enumeration.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

drivers/usb/host/ehci-hcd.c

@@ -52,7 +52,7 @@ static struct descriptor {
 		0x29,		/* bDescriptorType: hub descriptor */
 		2,		/* bNrPorts -- runtime modified */
 		0,		/* wHubCharacteristics */
-		0xff,		/* bPwrOn2PwrGood */
+		10,		/* bPwrOn2PwrGood */
 		0,		/* bHubCntrCurrent */
 		{},		/* Device removable */
 		{}		/* at most 7 ports! XXX */