Add some basic .gitignore files

This still leaves driver and architecture-specific subdirectories alone,
but gets rid of the bulk of the "generic" generated files that we should
ignore.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

scripts/mod/.gitignore

@@ -0,0 +1,4 @@
+elfconfig.h
+mk_elfconfig
+modpost
+