SMP: Add arch-agnostic boot_cpu()

We should not have x86 specific includes in lib/.

Change-Id: I18fa9c8017d65c166ffd465038d71f35b30d6f3d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/5156
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/lib/timestamp.c

@@ -23,7 +23,7 @@
 #include <cbmem.h>
 #include <timestamp.h>
 #include <arch/early_variables.h>
-#include <cpu/x86/lapic.h>
+#include <smp/node.h>
 
 #define MAX_TIMESTAMPS 30