Extend FIP io driver to support multiple FIP devices

Extend FIP io driver to support multiple FIP devices

Platform can define MAX_NUM_FIP_DEVICES in platform_def.h
to define the number of FIP io devices.

The FIP driver doesn't support muliple open file.
So only one single file can be open at a time across
multiple FIP devices.

For any FIP device, an image should be loaded
fully before moving on to the next image.

Signed-off-by: Ruchika Gupta <ruchika.gupta@nxp.com>