This file already uses sysfs_emit(). So be consistent and also use
sysfs_emit_at().

Moreover, size is always < PAGE_SIZE because scnprintf() (and now
sysfs_emit_at()) returns the number of characters written not including the
trailing '\0'. So some tests can be removed.

This slightly simplifies the code and makes it more readable.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Helge Deller <deller@gmx.de>