arm/oeqa/fvp: show more log from the FVP on failure

If the FVP fails to boot, the last 20 lines may just be a stack trace.
Show the last 200 lines for further context.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/lib/oeqa/controllers/fvp.py

@@ -63,7 +63,8 @@ class OEFVPTarget(oeqa.core.target.ssh.OESSHTarget):
                 return
         except asyncio.TimeoutError:
             self.logger.info("Timed out waiting for login prompt.")
-        self.logger.info(b"\n".join(bootlog.splitlines()[-20:]).decode("utf-8", errors="replace"))
+        self.logger.info("Boot log follows:")
+        self.logger.info(b"\n".join(bootlog.splitlines()[-200:]).decode("utf-8", errors="replace"))
         raise RuntimeError("Failed to start FVP.")
 
     def start(self, **kwargs):