scsi: pmcraid: Remove the PMCRAID_PASSTHROUGH_IOCTL ioctl implementation

The whole passthrough ioctl path looks completely broken. For example it
DMA maps the scatterlist and after that copies data to it, which is
prohibited by the DMA API contract.

Moreover, in pmcraid_alloc_sglist(), the pointer returned by a
sgl_alloc_order() call is not recorded anywhere which is pointless.

So remove the PMCRAID_PASSTHROUGH_IOCTL ioctl implementation entirely.
Should it be needed, we should reimplement it using the proper block layer
request mapping helpers.

Link: https://lore.kernel.org/r/7f27a70bec3f3dcaf46a29b1c630edd4792e71c0.1648298857.git.christophe.jaillet@wanadoo.fr


Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>