i2o: dbg: implemented an initial debug module.

Core debug:
i2o-debug.c contains a debugging module to debug the I2O core module. It
will be used to test all of its key features such as xfers and the sysfs
functionality.

This version is an initial version, more test cases will be added over
time.

Compile process:
Added the I2O subsystem to the staging subsystem Makefile. This way, the
module's will also be build correctly if a command like `make modules'
is invoked.

Signed-off-by: Michel Megens <dev@michelmegens.net>