Don't include errno.h from spawn.h

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

include/spawn.h

@@ -31,7 +31,6 @@
 
 #include <sched.h>
 #include <signal.h>
-#include <errno.h>
 
 /****************************************************************************
  * Pre-processor Definitions

sched/task/task_posixspawn.c

@@ -27,6 +27,7 @@
 #include <sys/wait.h>
 #include <spawn.h>
 #include <debug.h>
+#include <errno.h>
 
 #include <nuttx/sched.h>
 #include <nuttx/kthread.h>

sched/task/task_spawn.c

@@ -28,6 +28,7 @@
 #include <sched.h>
 #include <spawn.h>
 #include <debug.h>
+#include <errno.h>
 
 #include <nuttx/sched.h>
 #include <nuttx/kthread.h>

sched/task/task_spawnparms.c

@@ -27,6 +27,7 @@
 #include <fcntl.h>
 #include <spawn.h>
 #include <debug.h>
+#include <errno.h>
 
 #include <nuttx/semaphore.h>
 #include <nuttx/signal.h>