Remove invalid check in avc and hevc dec

If outBuffer is specificed, displayStride is the stride of the
outBuffer (line 526 for avc and line 521 for hevc). Then, the
"Output buffer too small" check ends up comparing a buffer's width
to the buffer's own stride which effectively requires that a
buffer's width is equal to it's stride.

For android.media.cts.DecoderTest#testCodecBasicHEVC, the test
has an outBuffer with width 720 and stride 768 which fails the
check.

Bug: b/146515640
Test: cts -t android.media.cts.DecoderTest
Change-Id: I732f77445cad5390895c8e43f46d11c423c9b2e4