[Zion] Enable SSE instructions at the start of boot.

These aren't ready to be used yet as we need to save them on task
switch.

zion/zion.cpp

@@ -1,6 +1,7 @@
 #include <stdint.h>
 
 #include "boot/acpi.h"
+#include "common/cpu.h"
 #include "common/gdt.h"
 #include "debug/debug.h"
 #include "interrupt/apic.h"
@@ -22,6 +23,8 @@ extern "C" void zion() {
   InitGdt();
   InitIdt();
 
+  ProbeCpuAndEnableFeatures();
+
   dbgln("[boot] Init Physical Memory Manager.");
   phys_mem::InitBootstrapPageAllocation();