backends: Use g_autofree in HostMemoryBackendClass::alloc() handlers

In preparation of having HostMemoryBackendClass::alloc() handlers
return a boolean, have them use g_autofree.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-Id: <20231120213301.24349-15-philmd@linaro.org>
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 361d4a8..fe8c481 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -44,8 +44,8 @@
                object_get_typename(OBJECT(backend)));
 #else
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
+    g_autofree gchar *name = NULL;
     uint32_t ram_flags;
-    gchar *name;
 
     if (!backend->size) {
         error_setg(errp, "can't create backend with size 0");
@@ -89,7 +89,6 @@
     memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), name,
                                      backend->size, fb->align, ram_flags,
                                      fb->mem_path, fb->offset, errp);
-    g_free(name);
 #endif
 }