i386: Add missing cpu feature bits in EPYC-Rome model

Found the following cpu feature bits missing from EPYC-Rome model.
ibrs    : Indirect Branch Restricted Speculation
ssbd    : Speculative Store Bypass Disable

These new features will be added in EPYC-Rome-v2. The -cpu help output
after the change.

x86 EPYC-Rome             (alias configured by machine type)
x86 EPYC-Rome-v1          AMD EPYC-Rome Processor
x86 EPYC-Rome-v2          AMD EPYC-Rome Processor

Reported-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Message-Id: <161478622280.16275.6399866734509127420.stgit@bmoger-ubuntu>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

target/i386/cpu.c

@@ -4179,6 +4179,18 @@ static X86CPUDefinition builtin_x86_defs[] = {
         .xlevel = 0x8000001E,
         .model_id = "AMD EPYC-Rome Processor",
         .cache_info = &epyc_rome_cache_info,
+        .versions = (X86CPUVersionDefinition[]) {
+            { .version = 1 },
+            {
+                .version = 2,
+                .props = (PropValue[]) {
+                    { "ibrs", "on" },
+                    { "amd-ssbd", "on" },
+                    { /* end of list */ }
+                }
+            },
+            { /* end of list */ }
+        }
     },
     {
         .name = "EPYC-Milan",