flashsv2enc: align codec declarations

While here constify enums for .pix_fmts.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/flashsv2enc.c

@@ -912,7 +912,7 @@ AVCodec ff_flashsv2_encoder = {
     .init           = flashsv2_encode_init,
     .encode2        = flashsv2_encode_frame,
     .close          = flashsv2_encode_end,
-    .pix_fmts = (enum PixelFormat[]) {PIX_FMT_BGR24, PIX_FMT_NONE},
-    .long_name = NULL_IF_CONFIG_SMALL("Flash Screen Video Version 2"),
-    .capabilities   =  CODEC_CAP_EXPERIMENTAL,
+    .pix_fmts       = (const enum PixelFormat[]){ PIX_FMT_BGR24, PIX_FMT_NONE },
+    .long_name      = NULL_IF_CONFIG_SMALL("Flash Screen Video Version 2"),
+    .capabilities   = CODEC_CAP_EXPERIMENTAL,
 };