[SCSI] sg: remove unnecessary check

coverity spotted this (cid #758).  All callers dereference sfp, so we dont
need this check.  In addition to this, we dereference it earlier in the
function.
Signed-off-by: NEric Sesterhenn <snakebyte@gmx.de>
Acked-by: NDouglas Gilbert <dougg@torque.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/sg.c

@@ -1842,7 +1842,7 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
 	int blk_size = buff_size;
 	struct page *p = NULL;
 
-	if ((blk_size < 0) || (!sfp))
+	if (blk_size < 0)
 		return -EFAULT;
 	if (0 == blk_size)
 		++blk_size;	/* don't know why */