hwpmc: further fix build (__diagused/debug/missing files entries)

Fix builds after 1459a22787ea16e3798694067c8dcb20325dca4b and
59191f3573f6cb2ea055ac319cbcb68823ca8e17 by using __diagused
for variables only used in KASSERT().
In addition remove two debug lines that look like a copy and paste error
from dmc620 to cmn600.
Further add the newly introduced files to sys/confg/files.arm64 as well
so that LINT compiles without missing symbols.