sound: usb: Issue stop endpoint command upon disable stream

Upon device disconnect, pending events on secondary event ring
are acknowledged as part of disable audio stream. It is observed
that few transfer events are posted by xHC after acknowledging
pending events. This results in to Host controller error(HCE)
when xHC is halted as part of xhci_suspend. Fix this issue by
explicitly issuing stop endpoint command upon receiving disable
audio stream request from remote entity.

Change-Id: I30efe037acddecadbac5bca4987ab45f78aa866b
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>