C2SoftAvcEnc: don't crash at unexpected input

Report failure instead of crash at input buffer size different than
what's configured.

Bug: 74073134
Test: adb shell setprop debug.stagefright.ccodec yes
Test: adb shell setprop debug.stagefright.omx_default_rank 1000
Test: adb shell killall mediaserver
Test: atest android.media.cts.MediaCodecTest
Change-Id: Id6c5eef205ae56f7b120cf5030630c7eabd8bc30
(cherry picked from commit fab635c8)