scsi: scsi_debug: Use vcalloc() to simplify code

Use vcalloc() instead of vmalloc() followed by bitmap_zero() to simplify
the function sdebug_add_store().

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Link: https://lore.kernel.org/r/20250806124633.383426-3-rongqianfeng@vivo.com


Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>