style(kernel): remove use of trailing return types

Although it looks nicer in my opinion, it appears that it is more
conventional to limit the use of `auto` to variable declarations and
other rare circumstances.

src/kernel/arch/i386/gdt.cpp

@@ -31,7 +31,7 @@ GlobalDescriptorTable::GlobalDescriptorTable()
 {
 }
 
-auto GlobalDescriptorTable::load() -> void
+void GlobalDescriptorTable::load()
 {
     // Define the size (limit) and start (base) of the descriptor table
     GlobalDescriptorTableRegister data = {
@@ -111,15 +111,15 @@ GlobalDescriptorTable::SegmentDescriptor::SegmentDescriptor(
     m_access_byte = options.access_byte;
 }
 
-auto GlobalDescriptorTable::SegmentDescriptor::base() const -> u32
+u32 GlobalDescriptorTable::SegmentDescriptor::base() const
 {
     u32 result = m_base_24_31;
     result = (result << 8) + m_base_16_23;
     result = (result << 16) + m_base_0_15;
     return result;
 }
 
-auto GlobalDescriptorTable::SegmentDescriptor::limit() const -> u32
+u32 GlobalDescriptorTable::SegmentDescriptor::limit() const
 {
     u32 result = m_flags_limit_16_19 & 0xF;
     result = (result << 16) + m_limit_0_15;

src/kernel/arch/i386/gdt.hpp

@@ -45,13 +45,13 @@ class GlobalDescriptorTable
         /**
          * The decoded linear address where this segment begins.
          */
-        [[nodiscard]] auto base() const -> u32;
+        u32 base() const;
 
         /**
          * The decoded limit of this segment, respecting the page granularity
          * such that it value ranges from 1 byte to 4 GiB.
          */
-        [[nodiscard]] auto limit() const -> u32;
+        u32 limit() const;
 
       private:
         SegmentDescriptor();
@@ -77,20 +77,20 @@ class GlobalDescriptorTable
     /**
      * Load the GlobalDescriptorTable by calling the LGDT instruction.
      */
-    auto load() -> void;
+    void load();
 
     /**
      * The raw value of the kernel code segment selector.
      */
-    auto code_segment_selector() const -> u16
+    u16 code_segment_selector() const
     {
         return (u8 *)&m_code_segment_selector - (u8 *)this;
     }
 
     /**
      * The raw value of the kernel data segment selector.
      */
-    auto data_segment_selector() const -> u16
+    u16 data_segment_selector() const
     {
         return (u8 *)&m_data_segment_selector - (u8 *)this;
     }