sw: Fix multi-cluster setting EOC correctly

Use cluster local core ID for determining which core is to set EOC instead of global one.
This fixes multi-cluster configurations not setting the EOC correctly on cluster != 0

Author: Smephite

sw/snRuntime/src/platforms/cheshire/start_snitch.S

@@ -15,7 +15,7 @@ _snrt_exit:
     addi      sp, sp, -8
     sw        a0, 0(sp)
     sw        ra, 4(sp)
-    call      snrt_global_core_idx
+    call      snrt_cluster_core_idx
     # reload exit code into t0
     lw        t0, 0(sp)
     lw        ra, 4(sp)

sw/snRuntime/src/platforms/standalone/start_snitch.S

@@ -15,7 +15,7 @@ _snrt_exit:
     addi      sp, sp, -8
     sw        a0, 0(sp)
     sw        ra, 4(sp)
-    call      snrt_global_core_idx
+    call      snrt_cluster_core_idx
     # reload exit code into t0
     lw        t0, 0(sp)
     lw        ra, 4(sp)