[libcpu] Fix CPUID register overwriting bug

Well god damnit, when i converted the `cpu::cpu_id::regs` struct to a
union, i was super sloppy and forgot to wrap the existing fields in
their own anonymous struct. I have been wrong about CPUID vales for
ages.

src/libraries/cpu/cpu/cpu_id.h

@@ -27,7 +27,9 @@ public:
     struct regs {
         union {
             uint32_t reg[4];
-            uint32_t eax, ebx, ecx, edx;
+            struct {
+                uint32_t eax, ebx, ecx, edx;
+            };
         };
 
         /// Return true if bit |bit| of EAX is set