refactor: replace in-tree Event Log Lib w/ submodule

The Event Log Library has been relocated to a separate repository and is
now integrated as a submodule, eliminating the need for in-tree files
and reducing maintenance efforts for TFTF.

Change-Id: I29694f8b3b08bb1d57dd685f6e42dc9f69d241bb
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
14 files changed