localmodconfig: Read in orig config file to avoid extra processing

Read in the entire config file. If there's a config that we depend on
that happens to be in the core set (not a module) then we do not need
to process it as a module.

Currently, we follow the entire depend and selects even if they
are enabled as core and not modules. By checking to make sure that we
only look at modules we can drop the count a little.

From one of my tests, localmodconfig went from taking 3095 set modules
down to 356 before this patch, and down to 290 modules after the change.

Tested-by: John David Yost <johnyost@ptd.net> # AlleyTrotter
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>