scsi: ibmvscsi_tgt: Fix dma_unmap_sg() nents value

scsi: ibmvscsi_tgt: Fix dma_unmap_sg() nents value

[ Upstream commit 023a293b9cd0bb86a9b50cd7688a3d9d266826db ]

The dma_unmap_sg() functions should be called with the same nents as the
dma_map_sg(), not the value the map function returned.

Fixes: 88a678bbc34c ("ibmvscsis: Initial commit of IBM VSCSI Tgt Driver")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Link: https://lore.kernel.org/r/20250630111803.94389-2-fourier.thomas@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>