misc: Use python f-strings for string formatting

This patch has been generated by applying flynt to the
gem5 repo (ext has been excluded)

JIRA: https://gem5.atlassian.net/browse/GEM5-831

Change-Id: I0935db6223d5426b99515959bde78e374cbadb04
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/68957
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>

src/python/m5/internal/params.py

@@ -50,4 +50,4 @@ except ImportError:
 if in_gem5:
     for name, module in inspect.getmembers(_m5):
         if name.startswith("param_") or name.startswith("enum_"):
-            exec("from _m5.%s import *" % name)
+            exec(f"from _m5.{name} import *")