trace: Fix alignment logic in flyrecord header

trace: Fix alignment logic in flyrecord header

Current alignment which is using 16 bytes is not correct in connection to
trace_clocks description and it's length.
That's why use start_addr variable and record proper size based on used
entries.

Fixes: d8dd439e9f95 ("trace: Update proftool to use new binary format").
Signed-off-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Simon Glass <sjg@chromium.org>