Make smc_plic.numberOfSources match top_matcha.h

Change-Id: I40a840585bdd85870600a19b01b6b71cafd059f2

platforms/smc.repl

diff --git a/platforms/smc.repl b/platforms/smc.repl
index a848c3d..368eab4 100644
--- a/platforms/smc.repl
+++ b/platforms/smc.repl
@@ -43,7 +43,7 @@
     // Bit 11 corresponds MEIP and bit 9 to SEIP.
     0 -> cpu1@11
     1 -> cpu1@9
-    numberOfSources: 15
+    numberOfSources: 16  // kTopMatchaPlicIrqIdLastSmc @ top_matcha.h
     numberOfContexts: 2  // MEIP and SEIP
 
 uart5: UART.OpenTitan_UART @ sysbus 0x50000000