debug: thread_analyzer: fix casting pointer to int warning

In thread_analyzer_auto(), it casts one function argument
directly into unsigned int. However, on 64-bit platforms,
the compiler complains about casting from pointer of
different size (-Wpointer-to-int-cast). So cast it first to
uintptr_t before casting it into unsigned int.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>