USB: host: ohci-at91: suspend: delay needed before to stop clocks

USB: host: ohci-at91: suspend: delay needed before to stop clocks

In order to completely remove marginal power consumption in PM suspend,
we need to let the controller settle down before being stopped.
In ohci_hcd_at91_drv_suspend() function, one additional delay is needed before
to stop the clocks.

Reported-by: Boris Krasnovskiy <Boris.Krasnovskiy@lairdconnect.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20190911064154.28633-3-nicolas.ferre@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>