linux-imx

arm64: Fix task tracing

For accurate accounting call contextidr_thread_switch before a
task is scheduled, rather than after, when the 'next' variable has a
different meaning since we switched the stacks.

Signed-off-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>