[SPARC64]: Move DCACHE_ALIASING_POSSIBLE define to asm/page.h

This showed that arch/sparc64/kernel/ptrace.c was not getting
the define properly, and thus the code protected by this ifdef
was never actually compiled before.  So fix that too.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/asm-sparc64/page.h b/include/asm-sparc64/page.h
index c9f8ef2..7f8d764 100644
--- a/include/asm-sparc64/page.h
+++ b/include/asm-sparc64/page.h
@@ -21,6 +21,13 @@
 #define PAGE_SIZE    (_AC(1,UL) << PAGE_SHIFT)
 #define PAGE_MASK    (~(PAGE_SIZE-1))
 
+/* Flushing for D-cache alias handling is only needed if
+ * the page size is smaller than 16K.
+ */
+#if PAGE_SHIFT < 14
+#define DCACHE_ALIASING_POSSIBLE
+#endif
+
 #ifdef __KERNEL__
 
 #ifndef __ASSEMBLY__