spapr: fix off-by-one error in spapr_ovec_populate_dt()

The last byte of the option vector was missing due to an off-by-one
error. Without this fix, client architecture support negotiation will
fail because the last byte of option vector 5, which contains the MMU
support, will be missed.
Signed-off-by: NSam Bobroff <sam.bobroff@au1.ibm.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NMichael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr_ovec.c

@@ -250,5 +250,5 @@ int spapr_ovec_populate_dt(void *fdt, int fdt_offset,
         }
     }
 
-    return fdt_setprop(fdt, fdt_offset, name, vec, vec_len);
+    return fdt_setprop(fdt, fdt_offset, name, vec, vec_len + 1);
 }