configs: Add ITS in fastmodel cluster

There's a gic-its domain in gem5_vexpress_v2 device tree, thus adding ITS
domain in fastmodel cluster config.

Change-Id: Ieb0221fec2e85710531cef1723c492a07f47290a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/62212
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Yu-hsin Wang <yuhsingw@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>

src/dev/arm/VExpressFastmodel.py

@@ -32,6 +32,8 @@ from m5.objects.SubSystem import SubSystem
 class VExpressFastmodel(VExpress_GEM5_Base):
     gic = FastModelGIC(
         sc_gic=SCFastModelGIC(
+            its_count=1,
+            its0_base=0x2E010000,
             reg_base=0x2C000000,
             reg_base_per_redistributor="0.0.0.0=0x2c010000",
             spi_count=988,