Settings: hide light pulse settings if not available

Instead of disabling the pulse length and speed hide them, since they
will not be enabled during the lifetime of the dialog

REF: CYNGNOS-426
Change-Id: Ie0c8b9f27e1de32c9559e5ffdb61c73d8b2ff42f
Signed-off-by: Roman Birg <roman@cyngn.com>