mm: nommu: fix a compile warning in do_mmap_pgoff()

Because 'ret' is declared as int, not unsigned long, no need to cast the
error contants into unsigned long.  If you compile this code on a 64-bit
machine somehow, you'll see following warning:

    CC      mm/nommu.o
  mm/nommu.c: In function `do_mmap_pgoff':
  mm/nommu.c:1411: warning: overflow in implicit constant conversion
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NGreg Ungerer <gerg@uclinux.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/nommu.c

@@ -1376,15 +1376,15 @@ unsigned long do_mmap_pgoff(struct file *file,
 		if (capabilities & BDI_CAP_MAP_DIRECT) {
 			addr = file->f_op->get_unmapped_area(file, addr, len,
 							     pgoff, flags);
-			if (IS_ERR((void *) addr)) {
+			if (IS_ERR_VALUE(addr)) {
 				ret = addr;
-				if (ret != (unsigned long) -ENOSYS)
+				if (ret != -ENOSYS)
 					goto error_just_free;
 
 				/* the driver refused to tell us where to site
 				 * the mapping so we'll have to attempt to copy
 				 * it */
-				ret = (unsigned long) -ENODEV;
+				ret = -ENODEV;
 				if (!(capabilities & BDI_CAP_MAP_COPY))
 					goto error_just_free;