x86: relocate_kernel - use PAGE_SIZE instead of numeric constant

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/relocate_kernel_64.S

@@ -159,7 +159,7 @@ relocate_new_kernel:
 	movq	%r9, %cr3
 
 	/* setup a new stack at the end of the physical control page */
-	lea	4096(%r8), %rsp
+	lea	PAGE_SIZE(%r8), %rsp
 
 	/* jump to identity mapped page */
 	addq	$(identity_mapped - relocate_kernel), %r8