common: fit: Update board_fit_image_post_process() to pass fit and node_offset

board_fit_image_post_process() passes only start and size of the image,
but type of the image is not passed. So pass fit and node_offset, to
derive information about image to be processed.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Tero Kristo <kristo@kernel.org>