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/hwc2_device/hwc2_device.cpp b/hwc2_device/hwc2_device.cpp
index a6dedb4..2242391 100644
--- a/hwc2_device/hwc2_device.cpp
+++ b/hwc2_device/hwc2_device.cpp
@@ -35,11 +35,11 @@
  * to the short "android::HwcLayer::SetLayerBuffer" for better logs readability
  */
 static std::string GetFuncName(const char *pretty_function) {
-  std::string str(pretty_function);
+  const std::string str(pretty_function);
   const char *start = "func = &";
-  size_t p1 = str.find(start);
+  auto p1 = str.find(start);
   p1 += strlen(start);
-  size_t p2 = str.find(',', p1);
+  auto p2 = str.find(',', p1);
   return str.substr(p1, p2 - p1);
 }
 
@@ -102,7 +102,7 @@
 static int HookDevClose(hw_device_t *dev) {
   // NOLINTNEXTLINE (cppcoreguidelines-pro-type-reinterpret-cast): Safe
   auto *hwc2_dev = reinterpret_cast<hwc2_device_t *>(dev);
-  std::unique_ptr<DrmHwcTwo> ctx(ToDrmHwcTwo(hwc2_dev));
+  const std::unique_ptr<DrmHwcTwo> ctx(ToDrmHwcTwo(hwc2_dev));
   return 0;
 }