migration: fix uninitialized variable warning in migrate_send_rp_req_…

…pages()

After the WITH_QEMU_LOCK_GUARD macro is added, the compiler cannot identify
 that the statements in the macro must be executed. As a result, some variables
 assignment statements in the macro may be considered as unexecuted by the compiler.

When the -Wmaybe-uninitialized capability is enabled on GCC9,the compiler showed warning:
migration/migration.c: In function ‘migrate_send_rp_req_pages’:
migration/migration.c:384:8: warning: ‘received’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 384 |     if (received) {
     |        ^

Add a default value for 'received' to prevented the warning.

Reported-by: Euler Robot <[email protected]>
Signed-off-by: Chen Qun <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Dr. David Alan Gilbert <[email protected]>

migration/migration.c

@@ -365,7 +365,7 @@ int migrate_send_rp_req_pages(MigrationIncomingState *mis,
                               RAMBlock *rb, ram_addr_t start, uint64_t haddr)
 {
     void *aligned = (void *)(uintptr_t)(haddr & (-qemu_ram_pagesize(rb)));
-    bool received;
+    bool received = false;
 
     WITH_QEMU_LOCK_GUARD(&mis->page_request_mutex) {
         received = ramblock_recv_bitmap_test_byte_offset(rb, start);