ion: use %pk instead of %p which respects kptr_restrict sysctl

Hide kernel pointers from unprivileged users by using %pk format-specifier
instead of %p. This respects the kptr_restrict sysctl setting which is by
default on. So by default %pk will print zeroes as address. echo 1 to
kptr_restrict to print proper kernel address.

Change-Id: Ia300e3e38b8662afac15edda28959564b05c9367
Signed-off-by: Satyajit Desai <sadesai@codeaurora.org>
Signed-off-by: Srinivasarao P <spathi@codeaurora.org>