amdgpu: Add .editorconfig file for amdgpu coding style

The .editorconfig file in the toplevel directory doesn't match.

Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/amdgpu/.editorconfig b/amdgpu/.editorconfig
new file mode 100644
index 0000000..2528d67
--- /dev/null
+++ b/amdgpu/.editorconfig
@@ -0,0 +1,9 @@
+# To use this config with your editor, follow the instructions at:
+# http://editorconfig.org
+
+[*]
+charset = utf-8
+indent_style = tab
+indent_size = 8
+tab_width = 8
+insert_final_newline = true