tests/si1133: add missing stdbool.h include

Fix compilation error on native platform where bool type is used but
stdbool.h is not explicitly included.

On many platforms (ARM, AVR, etc.), stdbool.h is indirectly included
via CPU headers, but on native this is not the case.

Signed-off-by: Gilles DOFFE <g.doffe@gmail.com>

tests/drivers/si1133/main.c

@@ -19,6 +19,7 @@
  */
 
 #include <stdio.h>
+#include <stdbool.h>
 #include <inttypes.h>
 
 #include "kernel_defines.h"