Revert "leds: triggers: Flush pending brightness before activating trigger"

This reverts commit 780785c7 which is
commit ab477b76 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: I8fd30165f96fac5a95987129282a9ecdb6315d38
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>