block: Fix misleading hexadecimal format

"0x%u" format is very misleading, replace by "0x%x".

Found running:

  $ git grep -E '0x%[0-9]*([lL]*|" ?PRI)[dDuU]' block/

Inspired-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Message-id: 20220323114718.58714-2-philippe.mathieu.daude@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/parallels-ext.c

@@ -261,7 +261,7 @@ static int parallels_parse_format_extension(BlockDriverState *bs,
             break;
 
         default:
-            error_setg(errp, "Unknown feature: 0x%" PRIu64, fh.magic);
+            error_setg(errp, "Unknown feature: 0x%" PRIx64, fh.magic);
             goto fail;
         }