ci: Change TF-M log level

Change the log level of TF-M so that the message that the CI is looking
for appears in the output.

Signed-off-by: Fabio Utzig <utzig@apache.org>
Change-Id: I763ccef4aaf6158ed578b230096f595a1e5cbfd9
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>