locking/refcount: Remove unused 'refcount_error_report()' function

'refcount_error_report()' has no callers. Remove it.

Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191121115902.2551-10-will@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>