nexus sim target: Add in IRQ mappings

Change-Id: I31574b0e4b1c56fa4e2be0454d1d4271a1086485

platforms/nexus.repl

diff --git a/platforms/nexus.repl b/platforms/nexus.repl
index 43c4607..6b768ab 100644
--- a/platforms/nexus.repl
+++ b/platforms/nexus.repl
@@ -30,3 +30,10 @@
 // ISP               [‘h4200_0000 - ‘h4200_FFFF)  64KB ISP registers
 // DMA Ctrl          [‘h4201_0000 - ‘h4201_FFFF)  64KB DMA control interface
 // DSP Ctrl          [‘h4202_0000 - ‘h4202_FFFF)  64KB Audio DSP control interface
+
+vec_controlblock : @ sysbus 0x5C000000
+    HostReqIRQ -> smc_plic@33
+    FinishIRQ -> smc_plic@34
+    InstructionFaultIRQ -> smc_plic@35
+    DataFaultIRQ -> smc_plic@36
+