[ot] scripts/opentitan: clang-tidy.yml: discard buggy rule

Discard a not so clever clang-tidy heuristic where

struct {
  struct { int a; int b; int c; } s;
  enum { x, y } e;
} foo;

triggers a 'bugprone-tagged-union-member-count' warning as clang-tidy
assumes that `enum e` selects one member in `struct s`!

Signed-off-by: Emmanuel Blot <[email protected]>

Author: rivos-eblot

scripts/opentitan/clang-tidy.yml

@@ -12,6 +12,7 @@ Checks:          '*,
                   -bugprone-implicit-widening-of-multiplication-result,
                   -bugprone-multi-level-implicit-pointer-conversion,
                   -bugprone-reserved-identifier,
+                  -bugprone-tagged-union-member-count,
                   -clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,
                   -clang-diagnostic-error,
                   -clang-diagnostic-unknown-warning-option,