We want to know if the 'vfp' property has been initialized.
Convert it from boolean to OptionalBool (which contain the
'unset' enum).

Note the monitor output is changed as:

  (qemu) info qtree
    ...
    dev: armv7m, id ""
      gpio-in "NMI" 1
      gpio-out "SYSRESETREQ" 1
      gpio-in "" 96
      clock-in "cpuclk" freq_hz=40 MHz
      clock-in "refclk" freq_hz=0 Hz
      cpu-type = "cortex-m33-arm-cpu"
      init-svtor = 270532608 (0x10200000)
      init-nsvtor = 0 (0x0)
      enable-bitband = false
      start-powered-off = false
-     vfp = false
+     vfp = "false"
      dsp = false
      mpu-ns-regions = 8 (0x8)
      mpu-s-regions = 8 (0x8)

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/arm/armv7m.h | 2 +-
 hw/arm/armsse.c         | 2 +-
 hw/arm/armv7m.c         | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/hw/arm/armv7m.h b/include/hw/arm/armv7m.h
index e2cebbd15c..6c9e65b644 100644
--- a/include/hw/arm/armv7m.h
+++ b/include/hw/arm/armv7m.h
@@ -105,7 +105,7 @@ struct ARMv7MState {
     uint32_t mpu_s_regions;
     bool enable_bitband;
     bool start_powered_off;
-    bool vfp;
+    OptionalBool vfp;
     bool dsp;
 };
 
diff --git a/hw/arm/armsse.c b/hw/arm/armsse.c
index 31acbf7347..472b16fc30 100644
--- a/hw/arm/armsse.c
+++ b/hw/arm/armsse.c
@@ -1028,7 +1028,7 @@ static void armsse_realize(DeviceState *dev, Error **errp)
             }
         }
         if (!s->cpu_fpu[i]) {
-            if (!object_property_set_bool(cpuobj, "vfp", false, errp)) {
+            if (!object_property_set_str(cpuobj, "vfp", "false", errp)) {
                 return;
             }
         }
diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
index d10abb36a8..3610f6f4a1 100644
--- a/hw/arm/armv7m.c
+++ b/hw/arm/armv7m.c
@@ -548,7 +548,7 @@ static Property armv7m_properties[] = {
     DEFINE_PROP_BOOL("enable-bitband", ARMv7MState, enable_bitband, false),
     DEFINE_PROP_BOOL("start-powered-off", ARMv7MState, start_powered_off,
                      false),
-    DEFINE_PROP_BOOL("vfp", ARMv7MState, vfp, true),
+    DEFINE_PROP_BOOL_NODEFAULT("vfp", ARMv7MState, vfp),
     DEFINE_PROP_BOOL("dsp", ARMv7MState, dsp, true),
     DEFINE_PROP_UINT32("mpu-ns-regions", ARMv7MState, mpu_ns_regions, UINT_MAX),
     DEFINE_PROP_UINT32("mpu-s-regions", ARMv7MState, mpu_s_regions, UINT_MAX),
-- 
2.41.0