camera2: add metadata private byte array.
camera2: add metadata private byte array.

This change adds a private byte array to the metadata
structure. This array is used to carry stream specific
metadata for the buffer, that can be used by other
streams.

Change-Id: I5055851167f344ba88948b17a49913122e22d2f0

maruos/android_device_lge_hammerhead,maruos/android_device_lge_hammerhead,maruos/android_device_lge_hammerhead,maruos/android_device_lge_hammerhead