fix potential mediaserver crash in ACodec::getPortFormat

https://issuetracker.google.com/issues/62428782



if rect.nLeft or rect.nTop is less then 0, in the error log it
will still check the integer overflow which probably cause abort

Test: NA

Change-Id: Ibe9a6edd0a57267b8dc7a29cdbdb2645e44c9af7
Signed-off-by: panshuangquan <panshuangquan@xiaomi.com>