.gitignore: Split into subdirectory files

There's no need for the global list of files to ignore, so use git's
ability to work with more local configuration.

Change-Id: I50882e6756cbc0fdfd899353cc23962544690fb3
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46879
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Christian Walter <christian.walter@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Documentation/.gitignore b/Documentation/.gitignore
new file mode 100644
index 0000000..a8f5d5f
--- /dev/null
+++ b/Documentation/.gitignore
@@ -0,0 +1,7 @@
+*.aux
+*.idx
+*.log
+*.toc
+*.out
+*.pdf
+_build