1. Update OSD palette config API. User must specify palette is default
or user defined.
2. OSD palette config will go through control and OSD data (region)
config will go through meta data in each frame.
3. Remove unused code.
4. Add mpi_enc_utils for mpi_enc_test cases
Change-Id: Ib4aeb60789a3e999446212841508e604533efb3c
Signed-off-by: Herman Chen <herman.chen@rock-chips.com>
