litex_json2renode: fix --bios-binary and add --opensbi-binary

--bios-binary is reverted to loading the bios into _rom_ as per the documentation and litex defaults
--opensbi-binary is added to load the openSBI binary into the opensbi memory region

The examples documented in the wiki now work again

litex/tools/litex_json2renode.py

@@ -883,16 +883,22 @@ def generate_resc(csr, number_of_cores, args, flash_binaries={}, tftp_binaries={
 """.format(cpu_type, args.repl)
 
     opensbi_base = csr['memories']['opensbi']['base'] if 'opensbi' in csr['memories'] else None
-    if opensbi_base is not None and args.bios_binary:
-        # load LiteX BIOS to ROM
+    if opensbi_base is not None and args.opensbi_binary:
+        # load OpenSBI to opensbi base
         result += """
 sysbus LoadBinary @{} {}
-""".format(args.bios_binary, hex(opensbi_base))
-
-    if opensbi_base:
+""".format(args.opensbi_binary, hex(opensbi_base))
         for cpu_id in range(0, number_of_cores):
             result += f"cpu{cpu_id} PC {hex(opensbi_base)}\n"
 
+    rom_base = csr['memories']['rom']['base'] if 'rom' in csr['memories'] else None
+    if rom_base is not None and args.bios_binary:
+        # load LiteX BIOS to ROM base
+        result += """
+sysbus LoadBinary @{} {}
+""".format(args.bios_binary, hex(rom_base))
+        result += f"cpu0 PC {hex(rom_base)}\n"
+
     if args.tftp_ip:
         result += """
 
@@ -1049,6 +1055,8 @@ def parse_args():
                         help='Generate virtual network and connect it to host')
     parser.add_argument('--bios-binary', action='store',
                         help='Path to the BIOS binary')
+    parser.add_argument('--opensbi-binary', action='store',
+                        help='Path to the OpenSBI binary')
     parser.add_argument('--firmware-binary', action='store',
                         help='Path to the binary to load into boot flash')
     parser.add_argument('--flash-binary', action='append', dest='flash_binaries_args',