tests: Fix a typo for the default MI_example protocol

Change-Id: I1c88ba45e4fee3c254db06cac46045dfe6e68524
Signed-off-by: Sean Wilson <spwilson2@wisc.edu>
Reviewed-on: https://gem5-review.googlesource.com/3795
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

tests/testing/tests.py

@@ -166,10 +166,7 @@ default_ruby_protocol = {
 }
 
 def get_default_protocol(arch):
-    try:
-        return default_ruby_protocol[arch]
-    except KeyError:
-        return 'MI-example'
+    return default_ruby_protocol.get(arch, 'MI_example')
 
 all_categories = ("quick", "long")
 all_modes = ("fs", "se")