microblaze: Add support from PREEMPT

This patch add core PREEMPT support for Microblaze.
I tried to trace it via tracers and I was able to see any output.

I also added low level debug functions to see if that code is called.

Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/asm-offsets.c

@@ -90,6 +90,7 @@ int main(int argc, char *argv[])
 	DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
 	DEFINE(TI_ADDR_LIMIT, offsetof(struct thread_info, addr_limit));
 	DEFINE(TI_CPU_CONTEXT, offsetof(struct thread_info, cpu_context));
+	DEFINE(TI_PREEMPT_COUNT, offsetof(struct thread_info, preempt_count));
 	BLANK();
 
 	/* struct cpu_context */