powerpc: Add macros to access floating point registers in thread_struct.

We are going to change where the floating point registers are stored
in the thread_struct, so in preparation add some macros to access the
floating point registers.  Update all code to use these new macros.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 7de41c3..582df704 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -110,7 +110,7 @@
 		return 0;
 	flush_fp_to_thread(current);
 
-	memcpy(fpregs, &tsk->thread.fpr[0], sizeof(*fpregs));
+	memcpy(fpregs, &tsk->thread.TS_FPR(0), sizeof(*fpregs));
 
 	return 1;
 }