Use sysfs_emit_at() instead of snprintf() + custom logic.
Using sysfs_emit_at() is much more simple.

Also, sysfs_emit() is already used in this function, so using
sysfs_emit_at() is more consistent.

Also simplify the logic:
  - always add a space after an entry
  - change the last space into a '\n'

Finally it is easy to see that, given the size of cabc_modes, PAGE_SIZE
can not be reached.
So better keep everything simple (and correct).
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>