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/memory.h

@@ -4,7 +4,6 @@
 EFI_STATUS memory_mark_address_for_update(void **pointer);
 
 EFI_STATUS memory_virtualize(
-	void **kernel_image,
 	EFI_MEMORY_DESCRIPTOR *memory_map,
 	UINTN memmap_size,
 	UINTN desc_size,