Revert "arm64: defer reloading a task's FPSIMD state to userland resume"

This reverts commit 41f7d22a.

This change results in occasional userspace crashes, presumably because
incorrect FPSIMD state is saved/restored. Revert it until the problems
are understood and fixed, resolving several merge conflicts along the
way.

Change-Id: I030c413950640aa6b83d55a8af5f75ab54ab9b7e
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>