KEYS: trusted: Debugging as a feature

TPM_DEBUG, and other similar flags, are a non-standard way to specify a
feature in Linux kernel.  Introduce CONFIG_TRUSTED_KEYS_DEBUG for
trusted keys, and use it to replace these ad-hoc feature flags.

Given that trusted keys debug dumps can contain sensitive data, harden
the feature as follows:

1. In the Kconfig description postulate that pr_debug() statements must be
   used.
2. Use pr_debug() statements in TPM 1.x driver to print the protocol dump.

Traces, when actually needed, can be easily enabled by providing
trusted.dyndbg='+p' in the kernel command-line.

Cc: Srish Srinivasan <ssrish@linux.ibm.com>
Reported-by: Nayna Jain <nayna@linux.ibm.com>
Closes: https://lore.kernel.org/all/7f8b8478-5cd8-4d97-bfd0-341fd5cf10f9@linux.ibm.com/
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v2:
- Implement for all trusted keys backends.
- Add HAVE_TRUSTED_KEYS_DEBUG as it is a good practice despite full
  coverage.