armv8r64-extras/oeqa: Remove greedy regex operator from Zephyr test

The ".*" at the end of the regex in the common check_boot() method in
the Zephyr test suite is greedy and may match more text than intended,
capturing text that was intended to match subsequent expects.

Remove the ".*" and just match on a static string.

Issue-Id: SCM-4957
Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Change-Id: I0bda762bd1eb54891f97e03b5e8aa15a487608ce