defconfig: sdm855: Enable USB function drivers

This change enables below mentioned different USB function drivers.
1. USB NCM
2. USB MTP
3. USB PTP
4. USB MIDI
5. USB Accessory
6. USB Audio Source

It enables USB gadget state related uevent notification to user space.
It also enables missing CONFIG_USB_ANNOUNCE_NEW_DEVICES with
sdm855_defconfig.

Change-Id: I3119946ff075839331c49a221386aa449bbf72a1
Signed-off-by: Mayank Rana <mrana@codeaurora.org>