localmodconfig: Add debug prints for dependencies of module configs

When a config for a module is added to the list to save in the final
config file, add a print to show what dependencies are used. This is
useful to debug when a config is disabled by the make oldconfig after
localmodconfig is finished.

This print only appears if the environment variable LOCALMODCONFIG_DEBUG
is defined.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>