[PATCH v4] qapi/qom: Memory backend property prealloc-threads doc fix

[Zhenyu Zhang]

Commit ffac16fab3 "hostmem: introduce "prealloc-threads" property"
(v5.0.0) changed the default number of threads from number of CPUs
to 1.  This was deemed a regression, and fixed in commit f8d426a685
"hostmem: default the amount of prealloc-threads to smp-cpus".
Except the documentation remained unchanged.

Update 'qapi/qom.json' to reflect the change in commit f8d426a6852c.

Signed-off-by: Zhenyu Zhang <zhenyzha@redhat.com>
---

v4: Fix the line exceeding 80 characters limitation issue  (Gavin)
v3: Covers historical descriptions                         (Markus)
v2: The property is changed to smp-cpus since 5.0          (Phild)

---
 qapi/qom.json | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/qapi/qom.json b/qapi/qom.json
index 30e76653ad..f4a7917f3d 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -576,7 +576,8 @@
 #
 # @prealloc: if true, preallocate memory (default: false)
 #
-# @prealloc-threads: number of CPU threads to use for prealloc (default: 1)
+# @prealloc-threads: number of CPU threads to use for prealloc 
+#                    (default: number of CPUs) (since 5.0)
 #
 # @prealloc-context: thread context to use for creation of preallocation 
threads
 #                    (default: none) (since 7.2)
-- 
2.31.1