USB: f_accessory: Set manufacturer and model string to default value

Currently USB driver is resetting strings like manufacturer, model
to zero as part of handling control request for protocol version. Some
accessory docks may not send manufacturer and model strings before sending
control request to enable audiosource USB composition. This results in
userspace enabling audio source composition without accessory interface.
If accessory dock is connected during bootup, accessory timeouts in
configuring android device and results in detection failure. Userspace does
have recovery mechanism if incase accessory dock timeouts to configure
android device in accessory composition. Hence set manufacturer and model
strings to default value so that userspace enables accessory + audiosource
composition for userspace recovery to be working and detecting accessory
dock successfully during bootup.

Change-Id: Ibe4dd9d951a9615ae100e68dc15b3614e9834848
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>