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

This reverts commit ac8f748c 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: I7b399962b7e16229efb0adf44a5583ae225e3274
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>