resources: Specify the number of cores to riscv platform

Due to a recent fix of HiFive platform,
https://gem5-review.googlesource.com/c/public/gem5/+/49431,
the number of cores must be explicitly specified.

Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Change-Id: I053e75ffb2c2d86da3478556599b70ecc45fdf49
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-resources/+/49630
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: Jason Lowe-Power <power.jg@gmail.com>
diff --git a/src/riscv-fs/configs/system/system.py b/src/riscv-fs/configs/system/system.py
index 3f545f1..85d162d 100755
--- a/src/riscv-fs/configs/system/system.py
+++ b/src/riscv-fs/configs/system/system.py
@@ -119,6 +119,9 @@
         # Create the memory controller
         self.createMemoryControllerDDR3()
 
+        # Set number of CPU cores
+        self.platform.setNumCores(num_cpus)
+
         self.setupInterrupts()
 
         # using RiscvLinux as the base full system workload