posix: Need sys/types.h to get suseconds_t defined

Picolibc's sys/_timeval.h (which Zephyr shouldn't be using) needs
sys/types.h to be included first so that __suseconds_t is defined.

Signed-off-by: Keith Packard <keithp@keithp.com>

include/zephyr/posix/sys/time.h

@@ -22,6 +22,7 @@ struct timeval {
 #endif
 
 #else
+#include <sys/types.h>
 #include <sys/_timeval.h>
 #endif /* CONFIG_NEWLIB_LIBC */