kernel/arch: consolidate tTCS and TNANO definitions

There was a lot of duplication between architectures for the definition
of threads and the "nanokernel" guts. These have been consolidated.

Now, a common file kernel/unified/include/kernel_structs.h holds the
common definitions. Architectures provide two files to complement it:
kernel_arch_data.h and kernel_arch_func.h. The first one contains at
least the struct _thread_arch and struct _kernel_arch data structures,
as well as the struct _callee_saved and struct _caller_saved register
layouts. The second file contains anything that needs what is provided
by the common stuff in kernel_structs.h. Those two files are only meant
to be included in kernel_structs.h in very specific locations.

The thread data structure has been separated into three major parts:
common struct _thread_base and struct k_thread, and arch-specific struct
_thread_arch. The first and third ones are included in the second.

The struct s_NANO data structure has been split into two: common struct
_kernel and arch-specific struct _kernel_arch. The latter is included in
the former.

Offsets files have also changed: nano_offsets.h has been renamed
kernel_offsets.h and is still included by the arch-specific offsets.c.
Also, since the thread and kernel data structures are now made of
sub-structures, offsets have to be added to make up the full offset.
Some of these additions have been consolidated in shorter symbols,
available from kernel/unified/include/offsets_short.h, which includes an
arch-specific offsets_arch_short.h. Most of the code include
offsets_short.h now instead of offsets.h.

Change-Id: I084645cb7e6db8db69aeaaf162963fe157045d5a
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
diff --git a/kernel/unified/idle.c b/kernel/unified/idle.c
index f388b66..b6e36a3 100644
--- a/kernel/unified/idle.c
+++ b/kernel/unified/idle.c
@@ -15,7 +15,7 @@
  */
 
 #include <nanokernel.h>
-#include <nano_private.h>
+#include <kernel_structs.h>
 #include <toolchain.h>
 #include <sections.h>
 #include <drivers/system_timer.h>
@@ -58,7 +58,7 @@
  */
 static void set_kernel_idle_time_in_ticks(int32_t ticks)
 {
-	_nanokernel.idle = ticks;
+	_kernel.idle = ticks;
 }
 #else
 #define set_kernel_idle_time_in_ticks(x) do { } while (0)