[SPARC64]: Fix FPU saving in 64-bit signal handling.

The calculation of the FPU reg save area pointer
was wrong.

Based upon an OOPS report from Tom Callaway.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/sparc64/kernel/signal.c

@@ -357,7 +357,7 @@ static int invalid_frame_pointer(void __user *fp, int fplen)
 static inline int
 save_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
 {
-	unsigned long *fpregs = (unsigned long *)(regs+1);
+	unsigned long *fpregs = current_thread_info()->fpregs;
 	unsigned long fprs;
 	int err = 0;