target-i386: Add range check for -cpu ,family=x

A family field value of 0xf and extended family field value of 0xff is
the maximum representable unsigned family number.
All other CPUID property values are bounds-checked, so add a check here
for symmetry before we adopt it in a property setter.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>

target-i386/cpu.c

@@ -691,7 +691,7 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
             if (!strcmp(featurestr, "family")) {
                 char *err;
                 numvalue = strtoul(val, &err, 0);
-                if (!*val || *err) {
+                if (!*val || *err || numvalue > 0xff + 0xf) {
                     fprintf(stderr, "bad numerical value %s\n", val);
                     goto error;
                 }