sparc64: Kill annoying warning when building compat_binfmt_elf.o

GCC warns because some tests against 32-bit values never evaluate to
true due to how TASK_SIZE is defined.

I always wanted to mimick powerpc's definition of TASK_SIZE, which
is simply TASK_SIZE_OF(current) and that also fixes the warning.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/sparc/include/asm/processor_64.h

@@ -36,10 +36,10 @@
 #define VPTE_SIZE	(1 << (VA_BITS - PAGE_SHIFT + 3))
 #endif
 
-#define TASK_SIZE	((unsigned long)-VPTE_SIZE)
 #define TASK_SIZE_OF(tsk) \
 	(test_tsk_thread_flag(tsk,TIF_32BIT) ? \
-	 (1UL << 32UL) : TASK_SIZE)
+	 (1UL << 32UL) : ((unsigned long)-VPTE_SIZE))
+#define TASK_SIZE	TASK_SIZE_OF(current)
 #ifdef __KERNEL__
 
 #define STACK_TOP32	((1UL << 32UL) - PAGE_SIZE)