PAX ASLR: convert debug messages to use KTR API

After this commit, you can debug ASLR with the KTR kernel options.
At run-time, you can read the log after enable PAX trace with KTR_PAX
mask (0x80000000): sysctl debug.ktr.mask=0x80000000, and you can read
the log via ktrdump command.

Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>