fix: spurious error log message with mem share test

Made a log line as VERBOSE to avoid an error log printed in the output,
in a test that was validating an FF-A error return.

Change-Id: Iae8192e91c437eec541b5a1fe64f647a4dad729b
Signed-off-by: J-Alves <joao.alves@arm.com>
1 file changed