drm_hwcomposer: CI: Bump-up clang toolchain to v15

Address new clang-tidy findings, in most cases 'misc-const-correctness'
check was addressed by adding 'const' modifier, or in some cases changed
to 'auto' (where it's better for formatting).

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/drm/DrmConnector.cpp b/drm/DrmConnector.cpp
index 4737316..69d029d 100644
--- a/drm/DrmConnector.cpp
+++ b/drm/DrmConnector.cpp
@@ -177,7 +177,7 @@
     }
 
     if (!exists) {
-      modes_.emplace_back(DrmMode(&connector_->modes[i]));
+      modes_.emplace_back(&connector_->modes[i]);
     }
   }