Kernel: Don't load AP init code to 0xF000, but relocate it later

This cleans up the kernel executable as bootloaders don't have to
load AP init code straight to 0xF000, but it will be moved there once
kernel is doing the AP initialization.

kernel/arch/i686/Signal.S

@@ -1,4 +1,4 @@
-.section .userspace, "aw"
+.section .userspace, "ax"
 
 // stack contains
 //    return address