usb: musb: Drop pointless PM runtime code for dsps glue

This already gets done automatically by PM runtime and we have
a separate autosuspend timeout in musb_core.c.

Reviewed-by: Johan Hovold <johan@kernel.org>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>