hw: Fix CVA6 debug module addresses (#173)

This fixes two errors in the debug module addresses passed to CVA6:

1. `HaltAddress` and `ExceptionAddress` are assumed to be relative to
`DmBaseAddress`, see
https://github.com/pulp-platform/cva6/blob/99ae53bde1a94b90c1d9bbbe7fe272a9336200a6/core/frontend/frontend.sv#L380
and
https://github.com/pulp-platform/cva6/blob/99ae53bde1a94b90c1d9bbbe7fe272a9336200a6/core/csr_regfile.sv#L2295.
Coincidentally, this currently does not cause any issues since `AmDbg = '0`,

2. `ExceptionAddress` was changed from `0x808` to `0x810` in
pulp-platform/riscv-dbg#145, which is included
in the debug module version used in Cheshire. This means that exceptions
in debug mode currently cause CVA6 to jump to `resume` and return from
debug mode instead of handling the exception, which breaks several
openocd commands that use exceptions to discover CSR availabilities.

Signed-off-by: Nils Wistoff <[email protected]>

hw/cheshire_pkg.sv

@@ -521,8 +521,8 @@ package cheshire_pkg;
       EnableAccelerator     : 0,
       RVS                   : 1,
       RVU                   : 1,
-      HaltAddress           : AmDbg + 'h800,
-      ExceptionAddress      : AmDbg + 'h808,
+      HaltAddress           : 'h800, // Relative to AmDbg
+      ExceptionAddress      : 'h810, // Relative to AmDbg
       RASDepth              : cfg.Cva6RASDepth,
       BTBEntries            : cfg.Cva6BTBEntries,
       BHTEntries            : cfg.Cva6BHTEntries,