Remove os_internal.h it has been replace by several new header files under sched/. There have been some sneak inclusion paths via os_internal.h, so expect a few compilation errors for some architectures

configs/xtrs/src/xtr_irq.c

@@ -42,7 +42,6 @@
 #include <nuttx/irq.h>
 
 #include "up_arch.h"
-#include "os_internal.h"
 #include "up_internal.h"
 
 /****************************************************************************

configs/xtrs/src/xtr_lowputc.c

@@ -48,7 +48,6 @@
 #include <assert.h>
 #include <debug.h>
 
-#include "os_internal.h"
 #include "up_internal.h"
 
 /* Includes trs80-m3.h for assembler call addresses */

configs/xtrs/src/xtr_serial.c

@@ -58,7 +58,6 @@
 #include <arch/z80/io.h>
 
 #include "up_arch.h"
-#include "os_internal.h"
 #include "up_internal.h"
 
 #ifdef USE_SERIALDRIVER