Revert "leds: trigger: Store brightness set by led_trigger_event()"

This reverts commit 2bc78ff2 which is
commit 822c91e7 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: If8dc383e04251ba799709f922a570097a65982ac
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>