media: venus: Refactor hfi_session_empty_buffer_compressed_pkt

The single element array data[1] is never used. Replace it with a
padding field of the same size.

This fixes the following cocci warning:
drivers/media/platform/qcom/venus/hfi_cmds.h:146:5-9: WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

)

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Acked-by: Vikash Garodia <quic_vgarodia@quicinc.com>
Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>