Fix armv7 compile with clang 4

With clang 4, the following error appears:

>   CC       criu/pie/parasite.o
> In file included from criu/pie/parasite.c:23:
> criu/arch/arm/include/asm/parasite.h:6:21: error: this function
> declaration is not a
>       prototype [-Werror,-Wstrict-prototypes]
>         *ptls = ((tls_t (*)())0xffff0fe0)();
>                            ^
>                             void
> 1 error generated.

Apparently, adding void fixes it.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/arch/arm/include/asm/parasite.h

@@ -3,7 +3,7 @@
 
 static inline void arch_get_tls(tls_t *ptls)
 {
-	*ptls = ((tls_t (*)())0xffff0fe0)();
+	*ptls = ((tls_t (*)(void))0xffff0fe0)();
 }
 
 #endif