compel ppc64 infect.c: fix clang compilation

This is generated by clang-3.8:
> compel/arch/ppc64/src/lib/infect.c:31:20: error: unused function
> '__check_code_syscall' [-Werror,-Wunused-function]
> static inline void __check_code_syscall(void)
>                    ^

The fix is the same as in commit 3ea2fd78.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

compel/arch/ppc64/src/lib/infect.c

@@ -28,7 +28,7 @@ const uint32_t code_syscall[] = {
 	0x0fe00000		/* twi 31,0,0	*/
 };
 
-static inline void __check_code_syscall(void)
+static inline __always_unused void __check_code_syscall(void)
 {
 	BUILD_BUG_ON(sizeof(code_syscall) != BUILTIN_SYSCALL_SIZE);
 	BUILD_BUG_ON(!is_log2(sizeof(code_syscall)));