add checkpatch config

- do not lint the submodule
- do not lint the grgsm code
- do not lint headers, checkpatch does not understand that this is a c++
project and any change to existing headers will cause issues.
- also do not do arcane C varargs checks that do not apply to C++

Change-Id: Ie7a9fbd021e12a88db30212240af2332c6cdcb37
diff --git a/.checkpatch.conf b/.checkpatch.conf
new file mode 100644
index 0000000..1e4b479
--- /dev/null
+++ b/.checkpatch.conf
@@ -0,0 +1,4 @@
+--exclude osmocom-bb/.*
+--exclude .*h
+--exclude Transceiver52M/grgsm_vitac/.*
+--ignore FUNCTION_WITHOUT_ARGS
\ No newline at end of file