vchiq: logging/tracing refactoring

• Create macros for error, info, warn, trace / debug
• Migrate existing printf() logging to use the above macros
• Add a sysctl knob to control it at runtime

This is based on work done in https://reviews.freebsd.org/D37878 .

Submitted by: Marco Devesas Campos <devesas.campos@gmail.com>
Differential Revision: https://reviews.freebsd.org/D53371