avcodec/qsvenc: clip global_quality for ICQ modes.

Allowed range is 1 to 51.

Ref: https://software.intel.com/content/www/us/en/develop/articles/advanced-bitrate-control-methods-in-intel-media-sdk.html

doc/encoders.texi

@@ -3119,7 +3119,8 @@ also set (the @option{-qscale} ffmpeg option).
 @option{look_ahead} option is also set.
 
 @item
-@var{ICQ} -- intelligent constant quality otherwise.
+@var{ICQ} -- intelligent constant quality otherwise. For the ICQ modes, global
+quality range is 1 to 51, with 1 being the best quality.
 @end itemize
 
 @item

libavcodec/qsvenc.c

@@ -650,7 +650,7 @@ static int init_video_param(AVCodecContext *avctx, QSVEncContext *q)
     case MFX_RATECONTROL_LA_ICQ:
         q->extco2.LookAheadDepth = q->look_ahead_depth;
     case MFX_RATECONTROL_ICQ:
-        q->param.mfx.ICQQuality  = avctx->global_quality;
+        q->param.mfx.ICQQuality  = av_clip(avctx->global_quality, 1, 51);
         break;
 #endif
 #endif