tests: fix CPUID detection tests compilation failure

In 3704b900 ("tests: Add CPU detection tests"), a macro called
DO_TEST_CPUID_JSON is added. But it took only two arguments when QEMU
or YAJL is not set.

Fix it by adding a third argument. Shouldn't have any effect because
that macro compiles to nothing.
Signed-off-by: NWei Liu <wei.liu2@citrix.com>

tests/cputest.c

@@ -700,7 +700,7 @@ mymain(void)
         }                                                               \
     } while (0)
 #else
-# define DO_TEST_CPUID_JSON(arch, host)
+# define DO_TEST_CPUID_JSON(arch, host, json)
 #endif
 
 #define DO_TEST_CPUID(arch, host, json)                                 \