intel/metadata/fit: spell out SACM to StartupACM

This makes it easier to grasp. Intel docs also spell it out. See:
https://www.intel.com/content/dam/develop/external/us/en/documents/firmware-interface-table-bios-specification-r1p2p1.pdf

Signed-off-by: Daniel Maslowski <info@orangecms.org>

Author: orangecms