usb: musb: Remove conditional PM runtime calls for musb_gadget

The conditional use of PM runtime does not work properly
for musb gadget. On cable disconnect we may not get any
USB_EVENT_NONE leaving the PM runtime call unpaired.

Let's fix the issue by making sure the PM runtime calls are
paired within the functions. The glue layer will take care
of the rest.

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>