libmix: fix klocwork issue in videoDecoderMPEG4

BZ: 73428

fix klocwork issue in VideoDecoderMPEG4, move check
to decodeFrame.
Signed-off-by: ywan171 <yi.a.wang@intel.com>

Change-Id: I927bd2931291e719c6bde19ac21c872a1a4e5393
Reviewed-on: http://android.intel.com:8080/86544
Reviewed-by: Wang, Yi A <yi.a.wang@intel.com>
Reviewed-by: Feng, Wei <wei.feng@intel.com>
Reviewed-by: Shi, PingX <pingx.shi@intel.com>
Tested-by: Shi, PingX <pingx.shi@intel.com>
Reviewed-by: cactus <cactus@intel.com>
Tested-by: cactus <cactus@intel.com>
1 file changed