arm/oeqa: Update FVP boot Linux transition to check for kernel panic

This commit addresses the exit condition when a kernel panic occurs
during boot. Previously, the Linux login expect command would wait until
the login prompt became available or until a timeout occurred. However,
if a kernel panic occurred, the test would unnecessarily wait until the
timeout trigger. With this commit, the test will now exit immediately if
a kernel panic occurs.

Signed-off-by: Divin Raj <divin.raj@arm.com>