Stop typecasting the value returned by kcalloc().

Link: https://lore.kernel.org/r/20201120083648.9319-1-vulab@iscas.ac.cnAcked-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>