Kernel: clean up include statements a bit

Coverity was flagging a recursive include between kernel.h and
cpulocals.h. As cpulocals.h also included proc.h, we can move that
include statement into kernel.h, and clean up the source files'
include statements accordingly.

kernel/kernel.h

@@ -45,8 +45,9 @@
 #include "ipc.h"		/* IPC constants */
 #include "profile.h"		/* system profiling */
 #include "perf.h"		/* performance-related definitions */
+#include "proc.h"		/* process table */
+#include "cpulocals.h"		/* CPU-local variables */
 #include "debug.h"		/* debugging, MUST be last kernel header */
-#include "cpulocals.h"
 
 #ifndef CONFIG_SMP
 /* We only support 1 cpu now */