usb: gadget: Do not allow ep request queuing when bus is not configured

USB Host driver can select any configuration that is presented by
peripheral driver to enable certian set of peripheral functions.
Till a particular configuration is selected, all peripheral function
drivers are considered to be disabled and any request to send/recevie
data is rejected. Allow only control endpoint(Ep0) queuing which is
used for advertise configurations and select a particular configuration.

Change-Id: I27cd8b2cc985aa16e2fd0de012b5eed4899f6d9a
CRs-fixed: 295668
Signed-off-by: Anji jonnala <anjir@codeaurora.org>