kcompactd_cpu_online() changes kcompactd cpumask, potentially
overwriting any vendor-specific cpumask that was there. This
hook allows vendors to re-set the cpumask.

Bug: 367400751
Bug: 369220046
Change-Id: I45b92bcd16fbf2d5d76474287db659e32af64201
Signed-off-by: Dmitry Skiba <dskiba@google.com>
(cherry picked from commit b3a2458f)