hvf: Determine slot count from struct layout

We can handle up to a static amount of memory slots, capped by the size of
an internal array.

Let's make sure that array size is the only source of truth for the number
of elements in that array.

Signed-off-by: Alexander Graf <agraf@csgraf.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211008054616.43828-1-agraf@csgraf.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/hvf/hvf-accel-ops.c

@@ -321,7 +321,7 @@ static int hvf_accel_init(MachineState *ms)
 
     s = g_new0(HVFState, 1);
 
-    s->num_slots = 32;
+    s->num_slots = ARRAY_SIZE(s->slots);
     for (x = 0; x < s->num_slots; ++x) {
         s->slots[x].size = 0;
         s->slots[x].slot_id = x;