[boot] Set up CR4 in bootloader

Moving the initial CR4 settings from the kernel's `memory_initialize`
(where it doesn't really fit anyway) to the bootloader's `hardware.cpp`.

src/boot/main.cpp

@@ -197,6 +197,7 @@ efi_main(uefi::handle image_handle, uefi::system_table *st)
 		L"Failed to exit boot services");
 
 	memory::virtualize(args->pml4, map, st->runtime_services);
+	hw::setup_cr4();
 
 	kentry(args);
 	debug_break();