usb: musb: core: controller drops session automatically

Whenever babble happens, MUSB controller will
drop session automatically.

The only case where it won't drop the session,
is when we're running on AM335x and SW_SESSION_CTRL
bit has been set. In that case, controller will
not touch session bit so SW has a chance to recover
from babble condition.

Tested-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>