Truly enable virtual memory.

Map is still identity-mapped. I think we need to sort and/or clean up
the map before using a higher half address. In-kernel vga output not
working yet, but do_the_set_registers() is getting called.

src/boot/loader.h

@@ -2,15 +2,15 @@
 #include <efi.h>
 
 #ifndef KERNEL_PHYS_ADDRESS
-#define KERNEL_PHYS_ADDRESS 0x0000000000100000
+#define KERNEL_PHYS_ADDRESS 0x100000
 #endif
 
 #ifndef KERNEL_VIRT_ADDRESS
-#define KERNEL_VIRT_ADDRESS 0x7fff000000000000
+#define KERNEL_VIRT_ADDRESS 0xf00000000
 #endif
 
 #ifndef KERNEL_MEMTYPE
-#define KERNEL_MEMTYPE 0xffffffff
+#define KERNEL_MEMTYPE 0x80000000
 #endif
 
 #ifndef KERNEL_FILENAME