parseutil: Use non ambiguous aliases for uhd

uhd1 and uhd2 would be ambigous.

doc/avconv.texi

@@ -497,9 +497,9 @@ abbreviations are recognized:
 2048x1080
 @item 4kdci
 4096x2160
-@item uhd1
+@item uhd2160
 3840x2160
-@item uhd2
+@item uhd4320
 7680x4320
 @end table
 

libavutil/parseutils.c

@@ -82,8 +82,8 @@ static const VideoSizeAbbr video_size_abbrs[] = {
     { "hd1080",   1920,1080 },
     { "2kdci",    2048,1080 },
     { "4kdci",    4096,2160 },
-    { "uhd1",     3840,2160 },
-    { "uhd2",     7680,4320 },
+    { "uhd2160",  3840,2160 },
+    { "uhd4320",  7680,4320 },
 };
 
 static const VideoRateAbbr video_rate_abbrs[]= {