st/nine: Protect *PrivateData also for Volumes

*PrivateData functions were not protected by
a mutex for Volumes whereas they definitely
should.

Signed-off-by: Axel Davy <davyaxel0@gmail.com>
Acked-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9177>

src/gallium/frontends/nine/nine_lock.c

@@ -3180,9 +3180,9 @@ IDirect3DVolume9Vtbl LockVolume9_vtable = {
     (void *)NineUnknown_AddRef,
     (void *)NineUnknown_ReleaseWithDtorLock,
     (void *)NineUnknown_GetDevice, /* actually part of Volume9 iface */
-    (void *)NineUnknown_SetPrivateData,
-    (void *)NineUnknown_GetPrivateData,
-    (void *)NineUnknown_FreePrivateData,
+    (void *)LockUnknown_SetPrivateData,
+    (void *)LockUnknown_GetPrivateData,
+    (void *)LockUnknown_FreePrivateData,
     (void *)LockVolume9_GetContainer,
     (void *)NineVolume9_GetDesc, /* immutable */
     (void *)LockVolume9_LockBox,