heif: Clamp display height and display width

The earlier code clamped the value of display width and display
height in FrameDecoder.cpp. This approach was incorrect because
display width and display height are allowed to be greater than
width and height respectively when being called from
MediaMetadataRetriever.getScaledFrameAtTime. It was causing the
cts tests to fail.

The correct fix is to clamp them in the HeifDecoder since the
original set of changes were to support cropping in Heif.

Bug: 316481431, 320331874
Test: atest android.security.cts.StagefrightTest CtsMediaMiscTestCases
Change-Id: I5d0fcd70a81c9d429f175b4ca529a2554f4f9883