Fix nptl/tst-cancel-self-cancelstate.c warning

[Ondřej Bílka]

On Wed, Nov 26, 2014 at 01:32:52PM +0000, Joseph Myers wrote:
> This patch fixes "../sysdeps/nptl/pthread.h:670:26: warning:
> initialization discards 'volatile' qualifier from pointer target type"
> arising when building nptl/tst-cancel-self-cancelstate.c.  The problem
> is passing a volatile int * to a macro expecting void *; the patch
> adds an explicit cast.
> 
ok.