USB: musb: only turn off vbus in OTG hosts

USB: musb: only turn off vbus in OTG hosts

Except on DaVinci, VBUS is now switched off as part of idling the
USB link (after a_wait_bcon) whenever a device is disconnected
from host.  This is correct for OTG hosts, where either SRP or
an ID interrupt could turn VBUS on again.

However, for non-OTG hosts there's no way to turn VBUS on again,
so the host becomes unusable.  And the procfs entry which once
allowed a manual workaround for this is now gone.

This patch adds an is_otg_enabled() check before scheduling the
switch-off timer in disconnect path, supporting a "classic host"
mode where SRP is unavailable.

[ dbrownell@users.sourceforge.net: tweak patch description ]

Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>