venus: Fix for H265 decoding failure.

Aligned the mismatch of persist1 and scratch1 buffer calculation,
as per the firmware requirements.

Signed-off-by: Vikash Garodia <vgarodia@qti.qualcomm.com>
Signed-off-by: Viswanath Boma <quic_vboma@quicinc.com>
Tested-by: Nathan Hebert <nhebert@chromium.org>
Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>