ANDROID: staging: ion: Obey kptr_restrict

The /sys/kernel/debug/ion/clients/<client> file could disobey the
setting of kptr_restrict if a client went away after the file started
to be accessed. Use %pK when printing the ion client to avoid this
problem.

Some other debugging messages also did not use %pK, but since those
messages are not very useful and have been removed upstream, just remove
them instead.

Bug: 77937819
Change-Id: Ie45897fe2d6ec3f842a02883e8ec929ed2e76933
Signed-off-by: Alistair Strachan <astrachan@google.com>