MLK-22078 romapi: Fix issue for stream mode with secure boot enabled

MLK-22078 romapi: Fix issue for stream mode with secure boot enabled

When download image through ROM API for stream mode (USB, eMMC fastboot).
We uses tricky way to get the total image size:
The spl_load_simple_fit is called but the data reading is invalid, so the image
data is not really downloaded.
We should not call HAB authenticate in this tricky way. Otherwise it
will alway fail.
This patch add a new flag SPL_FIT_BYPASS_POST_LOAD to skip the authentication
only for this tricky using.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
(cherry picked from commit 47b0cf6de06ff9b3e2b2755d5c8203210378b26a)