edac: arm64: Enable cti pmu workaround on CPUs onlined post-boot

The CTI PMU workaround for the EDAC interrupt is enabled at probe
only on the CPUs that are online during boot-up. Some of the CPUs
can be onlined at a later point from userspace.
Ensure that the workaround is enabled on those CPUs as well.

Change-Id: I551b228d3df3f7ed7d935a55aec6474339d569a6
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>