avfilter/vf_transpose: Don't call av_pix_fmt_desc_get() twice

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavfilter/vf_transpose.c

@@ -55,10 +55,10 @@ typedef struct TransContext {
 static int query_formats(AVFilterContext *ctx)
 {
     AVFilterFormats *pix_fmts = NULL;
+    const AVPixFmtDescriptor *desc;
     int fmt, ret;
 
-    for (fmt = 0; av_pix_fmt_desc_get(fmt); fmt++) {
-        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(fmt);
+    for (fmt = 0; desc = av_pix_fmt_desc_get(fmt); fmt++) {
         if (!(desc->flags & AV_PIX_FMT_FLAG_PAL ||
               desc->flags & AV_PIX_FMT_FLAG_HWACCEL ||
               desc->flags & AV_PIX_FMT_FLAG_BITSTREAM ||