usb: musb: try a race-free wakeup

usb: musb: try a race-free wakeup

Attaching a keyboard, using it as a wakeup via
|for f in $(find /sys/devices/ocp.3/47400000.usb -name wakeup)
|do
|	echo enabled > $f
|done

going into standby
|  echo standby >  /sys/power/state

and now a wake up by a pressing a key.
What happens is that the system wakes up but the USB device is dead. The
USB stack tries to send a few control URBs but nothing comes back.
Eventually it gaves up and the device remains dead:
|[  632.559678] PM: Wakeup source USB1_PHY
|[  632.581074] PM: noirq resume of devices complete after 21.261 msecs
|[  632.607521] PM: early resume of devices complete after 10.360 msecs
|[  632.616854] net eth2: initializing cpsw version 1.12 (0)
|[  632.704126] net eth2: phy found : id is : 0x4dd074
|[  636.704048] libphy: 4a101000.mdio:00 - Link is Up - 1000/Full
|[  638.444620] usb 1-1: reset low-speed USB device number 2 using musb-hdrc
|[  653.713435] usb 1-1: device descriptor read/64, error -110
|[  669.093435] usb 1-1: device descriptor read/64, error -110
|[  669.473424] usb 1-1: reset low-speed USB device number 2 using musb-hdrc
|[  684.743436] usb 1-1: device descriptor read/64, error -110
|[  690.065097] PM: resume of devices complete after 57450.744 msecs
|[  690.076601] PM: Finishing wakeup.
|[  690.076627] Restarting tasks ...

It seems that since we got woken up via MUSB_INTR_RESUME the
musb_host_finish_resume() callback is executed before the
resume-callbacks of the PHY and glue layer are invoked. If I delay it
until the glue layer resumed then I don't see this problem.

I also move musb_host_resume_root_hub() into that callback since I don't
see any reason in doing anything resume-link if there are still pieces
not restored.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>