cheriot: load firmware image symbols into simulator

In particular this enables the simulator to identify when the simulation
signals termination by writing to "tohost".

Bypass-Presubmit-Reason: no sencha tests

Change-Id: I897c0d67f578307bb3ce9fe3822ab4cfa3440a9d

cheriot.resc

diff --git a/cheriot.resc b/cheriot.resc
index bc9633d..bf8b901 100644
--- a/cheriot.resc
+++ b/cheriot.resc
@@ -49,4 +49,6 @@
 # Load the ELF file (useVirtualAddress = false, allowLoadsOnlyToMemory = false)
 sysbus LoadELF $bin false false
 
+sysbus.cpu1 SymbolFile $bin
 sysbus.cpu1 IsHalted false
+