Revert "tasklet: Introduce new initialization API"

This reverts commit 21dc5a1d which is
commit 12cc923f 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: Iefe5dc5762b9c1645414301ecab9e35c1e79f78f
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>