Kernel: Fix Processor::features_string() stopping too early and detect more features

The exit condition for the loop was sizeof(m_features) * 8,
which was 32. Presumably this was supposed to mean 32 bits, but it
actually made it stop as soon as it reached the 6th bit.

Also add detection for more SIMD CPU features.

Kernel/Arch/i386/CPU.h

@@ -591,6 +591,7 @@ private:
     SplitQword m_start;
 };
 
+// FIXME: This can't hold every CPU feature as-is.
 enum class CPUFeature : u32 {
     NX = (1 << 0),
     PAE = (1 << 1),
@@ -603,7 +604,13 @@ enum class CPUFeature : u32 {
     TSC = (1 << 8),
     UMIP = (1 << 9),
     SEP = (1 << 10),
-    SYSCALL = (1 << 11)
+    SYSCALL = (1 << 11),
+    MMX = (1 << 12),
+    SSE2 = (1 << 13),
+    SSE3 = (1 << 14),
+    SSSE3 = (1 << 15),
+    SSE4_1 = (1 << 16),
+    SSE4_2 = (1 << 17)
 };
 
 class Thread;