tools/objtool: Copy the __cleanup unused variable fix for older clang

tools/objtool: Copy the __cleanup unused variable fix for older clang

Copy from

  54da6a092431 ("locking: Introduce __cleanup() based infrastructure")

the bits which mark the variable with a cleanup attribute unused so that my
clang 15 can dispose of it properly instead of warning that it is unused which
then fails the build due to -Werror.

Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20251031114919.GBaQSiPxZrziOs3RCW@fat_crate.local