sched: Don't include nuttx/sched.h inside sched.h

But let nuttx/sched.h include sched.h instead to
avoid expose nuttx kernel API to userspace.

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

graphics/vnc/server/vnc_fbdev.c

@@ -27,6 +27,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 #include <errno.h>
 
 #if defined(CONFIG_VNCSERVER_DEBUG) && !defined(CONFIG_DEBUG_GRAPHICS)