configs: Add import for FileSystemConfig in GPU_VIPER.py

GPU_VIPER.py uses FileSystemConfig to register CPUs and caches in SE
mode. Without the import, it crashes.

Change-Id: I539a4060d705f6e1b9a12aca7836eca271f61557
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/32675
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/ruby/GPU_VIPER.py

@@ -37,6 +37,7 @@ from m5.defines import buildEnv
 from m5.util import addToPath
 from .Ruby import create_topology
 from .Ruby import send_evicts
+from common import FileSystemConfig
 
 addToPath('../')