Recent runtime pm and hwmod conversions for 2.6.39 broke the musb peripheral
mode OMAP retention idle on boards where the board mode in struct
musb_hdrc_platform_data is set to MUSB_PERIPHERAL.

These conversions changed the way how the OTG_SYSCONFIG register is
configured and used in runtime. Before 2.6.39 smart standby/idle modes were
activated statically in OTG_SYSCONFIG. Those modes allow that the musb is
able to idle when peripheral device is not connected to host.

In 2.6.39 the OTG_SYSCONFIG is updated runtime depending on VBUS status.
No standby/idle modes are used when device is connected and force
standby/idle when disconnected.

Unfortunately VBUS disconnect event that handles the disconnect case lets
the peripheral musb to idle only when board mode is MUSB_OTG. Fix this by
checking the peripheral mode also.

Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>