Kernel: Use enum instead of magic numbers for GDT descriptor types

Some of the enum members were also renamed to reflect the fact that the
segment sizes are not necessarily 32bit (64bit on x86_64).

Kernel/Arch/x86/DescriptorTable.h

@@ -66,7 +66,7 @@ union [[gnu::packed]] Descriptor {
         u32 high;
     };
 
-    enum Type {
+    enum SystemType {
         Invalid = 0,
         AvailableTSS_16bit = 0x1,
         LDT = 0x2,
@@ -75,11 +75,11 @@ union [[gnu::packed]] Descriptor {
         TaskGate = 0x5,
         InterruptGate_16bit = 0x6,
         TrapGate_16bit = 0x7,
-        AvailableTSS_32bit = 0x9,
-        BusyTSS_32bit = 0xb,
-        CallGate_32bit = 0xc,
-        InterruptGate_32bit = 0xe,
-        TrapGate_32bit = 0xf,
+        AvailableTSS = 0x9,
+        BusyTSS = 0xb,
+        CallGate = 0xc,
+        InterruptGate = 0xe,
+        TrapGate = 0xf,
     };
 
     VirtualAddress base() const

Kernel/Arch/x86/common/Processor.cpp

@@ -1222,7 +1222,7 @@ UNMAP_AFTER_INIT void Processor::gdt_init()
     tss_descriptor.operation_size64 = 0;
     tss_descriptor.operation_size32 = 1;
     tss_descriptor.descriptor_type = 0;
-    tss_descriptor.type = 9;
+    tss_descriptor.type = Descriptor::SystemType::AvailableTSS;
     write_gdt_entry(GDT_SELECTOR_TSS, tss_descriptor); // tss
 
 #if ARCH(X86_64)