ppc64: Allocate the first segment separately

arch/ppc64/kernel/head.S

@@ -1824,10 +1824,10 @@ ioremap_dir:
 hardware_int_paca0:
 	.space	8*4096
 
-/* 1 page segment table per cpu (max 48) */
+/* 1 page segment table per cpu (max 48, cpu0 allocated at 0x5000) */
 	.globl	stab_array
 stab_array:
-	.space	4096 * 48
+	.space	4096 * 47
 	
 /*
  * This space gets a copy of optional info passed to us by the bootstrap