hwc: HWC 2.0 implementation

Add HWCLayer, HWCCallbacks and implement HWC2 layer functionality.

Change-Id: Ic7764e72f4cae534e68764df4cf80eb3db982071
diff --git a/sdm/.clang-format b/sdm/.clang-format
new file mode 100644
index 0000000..9082c40
--- /dev/null
+++ b/sdm/.clang-format
@@ -0,0 +1,13 @@
+---
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