media: venus: hfi: add Host Firmware Interface (HFI)

This is the implementation of HFI. It is charged with the
responsibility to comunicate with the firmware through an
interface commands and messages.

 - hfi.c has interface functions used by the core, decoder
and encoder parts to comunicate with the firmware. For example
there are functions for session and core initialisation.

 - hfi_cmds has packetization operations which preparing
packets to be send from host to firmware.

 - hfi_msgs takes care of messages sent from firmware to the
host.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>