Fix coverity defects
coverity scan CID:147633,type: sizeof not portable
coverity scan CID:147637,type: sizeof not portable
coverity scan CID:147638,type: sizeof not portable
coverity scan CID:147640,type: sizeof not portable
In these particular cases sizeof (XX **) happens to be equal to sizeof (X *),
but this is not a portable assumption.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: luozhengzheng <luo.zhengzheng@zte.com.cn>
Closes #5144