Remove the comment above ioctl_internal_command() which doesn't document
this function at all.

Link: https://lore.kernel.org/r/20210724072033.1284840-21-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>