checkpatch: add .checkpatch.conf

Try to make checkpatch a little friendlier to the coreboot project.

This is the checkpatch .conf from the Chrome OS tree.

Change-Id: Ie45d5c93f97bd58f3ea31341b47c4ee2a8f02b1e
Signed-off-by: Martin Roth <martinroth@chromium.org>
Reviewed-on: https://review.coreboot.org/15919
Tested-by: build bot (Jenkins)
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

.checkpatch.conf

@@ -0,0 +1,16 @@
+# Not Linux, so don't expect a Linux tree.
+--no-tree
+
+# Require every Kconfig symbol to have at least two lines in their description.
+--min-conf-desc-length=2
+
+# Ignore aspects we don't follow here.
+--ignore C99_COMMENTS
+--ignore GLOBAL_INITIALISERS
+--ignore INITIALISED_STATIC
+--ignore LINE_SPACING
+--ignore NEW_TYPEDEFS
+--ignore PREFER_ALIGNED
+--ignore PREFER_PACKED
+--ignore PREFER_PRINTF
+--ignore SPLIT_STRING