x86: eliminate hard-coded constants

Index: 2007-11-13/xen/arch/x86/boot/head.S
===================================================================
@@ -168,7 +168,7 @@ __start:
         mov     $trampoline_end - trampoline_start,%ecx
         rep     movsb
 
-        mov     $0x90000,%esp
+        mov     $sym_phys(wakeup_stack),%esp
         call    cmdline_parse_early
 
         /* Jump into the relocated trampoline. */

Index: 2007-11-13/xen/arch/x86/boot/trampoline.S
===================================================================
@@ -150,8 +150,8 @@ trampoline_boot_cpu_entry:
         mov     %ax,%es
         mov     %ax,%ss
 
-        /* Stack grows down from +0x3000. Initialise IDT and enable irqs. */
-        mov     $0x3000,%sp
+        /* Initialise stack pointer and IDT, and enable irqs. */
+        mov     $bootsym(wakeup_stack),%sp
         lidt    bootsym(rm_idt)
         sti
 

Index: 2007-11-13/xen/arch/x86/boot/video.S
===================================================================
@@ -15,8 +15,8 @@
 
 #include "video.h"
 
-/* Scratch space layout: +0x3000 to +0x4000. */
-#define modelist       (0x3000)                  /* 2kB (256 entries) */
+/* Scratch space layout: trampoline_end to trampoline_end+0x1000. */
+#define modelist       bootsym(trampoline_end)   /* 2kB (256 entries) */
 #define vesa_glob_info (modelist + 0x800)        /* 1kB */
 #define vesa_mode_info (vesa_glob_info + 0x400)  /* 1kB */