media: vicodec: Add a flag for I-frames in fwht header

Add a flag 'FWHT_FL_I_FRAME' that indicates that
this is an I-frame. This requires incrementing
to version 3

This flag is needed for the upcoming stateless FWHT
decoder since it has to know if an encoded frame is
an I or a P frame.

Signed-off-by: Dafna Hirschfeld <dafna3@gmail.com>
[hverkuil-cisco@xs4all.nl: added the last paragraph of the commit msg]
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>