libpayload: Force checking all EHCI ports on power-on

EHCI port status reporting isn't very consistent on power-on,
so just looking for devices on all ports is the safest way to
find everything.

Change-Id: I26b4305016f0bed1d2c1b5cffc59d5813fa1cbbb
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/594
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marcj303@gmail.com>

payloads/libpayload/drivers/usb/ehci_rh.c

@@ -147,6 +147,7 @@ ehci_rh_init (usbdev_t *dev)
 		p = &(RH_INST(dev)->ports[i]);
 		RH_INST(dev)->devices[i] = -1;
 		*p |= P_PP;
+		ehci_rh_scanport(dev, i);
 	}
 
 	dev->address = 0;