Change lock to lockYCbCr for to get the actual y,cb,cr.

Found when use google sw decoder,below CTS case will fail:
CtsMediaTestCases android.media.cts.DecodeAccuracyTest 8,12,24,28,40,44.
Checked the failed case,test video height is not 4 bytes align,
eg 426x182,854x362,1920x818.
Some platform GPU may need height 4 bytes align, so the dst_v,dst_u calculation
should consider height alignment.
Here change lock to lockYCbCr to get the actual y,cb,cr.

Change-Id: Ibbccbad3936ab36ee2c25773367b0fbb67d9226e
Signed-off-by: Jessie Hao <juan.hao@nxp.com>