usb: musb: Handle cable status better for 2430 glue layer

We may have drivers loaded but no configured gadgets and MUSB may be in
host mode. If gadgets are configured during host mode, PM runtime will
get confused.

Disable PM runtime from gadget state, and do it based on the cable
and last state.

Note that we may get multiple cable events, so we need to keep track
of the power state.

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>