Remove some unnecessary header file inclusions

drivers/ioexpander/gpio_lower_half.c

@@ -40,8 +40,6 @@
 #include <nuttx/config.h>
 
 #include <sys/types.h>
-#include <stdio.h>
-#include <signal.h>
 #include <assert.h>
 #include <errno.h>