vhost-scsi: Fix check for inline_sg_cnt exceeding preallocated limit

The condition comparing ret to VHOST_SCSI_PREALLOC_SGLS was incorrect,
as ret holds the result of kstrtouint() (typically 0 on success),
not the parsed value. Update the check to use cnt, which contains the
actual user-provided value.

prevents silently accepting values exceeding the maximum inline_sg_cnt.

Fixes: bca939d5 ("vhost-scsi: Dynamically allocate scatterlists")
Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20250628183405.3979538-1-alok.a.tiwari@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>