Revert: "dell-laptop: Toggle the unsupported hardware killswitch"

This reverts commit a3d77411,

as it causes a mess in the wireless rfkill status on some models.
It is probably a bad idea to toggle the rfkill for all dell models
without the respect to the claim that it is hardware-controlled.

Cc: stable@kernel.org
Signed-off-by: Keng-Yu Lin <kengyu@canonical.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>