refactor(measured-boot): accept metadata as a function's argument

Updated the event log driver's function to accept metadata as an
argument, to remove the platform function usage from the event log
driver to make it a standalone driver.

Change-Id: I512cf693d51dc3c0b9d2c1bfde4f89414e273049
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
2 files changed