sysfs: return correct error code on unimplemented mmap()

Both POSIX.1-2008 and Linux Programmer's Manual have a dedicated return
error code for a case, when a file doesn't support mmap(), it's ENODEV.

This change replaces overloaded EINVAL with ENODEV in a situation
described above for sysfs binary files.

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/sysfs/file.c

@@ -477,7 +477,6 @@ static int sysfs_bin_mmap(struct file *file, struct vm_area_struct *vma)
 	if (!sysfs_get_active(of->sd))
 		goto out_unlock;
 
-	rc = -EINVAL;
 	if (!battr->mmap)
 		goto out_put;