Remove unreal mode code from boot.s

We can do this later in the second stage.

Author: phil-opp

real_mode/first_stage/src/boot.s

@@ -30,40 +30,6 @@ enable_a20:
     out 0x92, al
 enable_a20_after:
 
-enter_protected_mode:
-    # clear interrupts
-    cli
-    push ds
-    push es
-
-    lgdt [gdt32info]
-
-    mov eax, cr0
-    or al, 1    # set protected mode bit
-    mov cr0, eax
-
-    jmp protected_mode                # tell 386/486 to not crash
-
-protected_mode:
-    mov bx, 0x10
-    mov ds, bx # set data segment
-    mov es, bx # set extra segment
-
-    and al, 0xfe    # clear protected mode bit
-    mov cr0, eax
-
-unreal_mode:
-    pop es # get back old extra segment
-    pop ds # get back old data segment
-    sti
-
-    # back to real mode, but internal data segment register is still loaded
-    # with gdt segment -> we can access the full 4GiB of memory
-
-    mov bx, 0x0f01         # attrib/char of smiley
-    mov eax, 0xb8f00       # note 32 bit offset
-    mov word ptr ds:[eax], bx
-
 check_int13h_extensions:
     push 'y'    # error code
     mov ah, 0x41
@@ -82,29 +48,3 @@ spin:
     hlt
     jmp spin
 
-gdt32info:
-   .word gdt32_end - gdt32 - 1  # last byte in table
-   .word gdt32                  # start of table
-
-gdt32:
-    # entry 0 is always unused
-    .quad 0
-codedesc:
-    .byte 0xff
-    .byte 0xff
-    .byte 0
-    .byte 0
-    .byte 0
-    .byte 0x9a
-    .byte 0xcf
-    .byte 0
-datadesc:
-    .byte 0xff
-    .byte 0xff
-    .byte 0
-    .byte 0
-    .byte 0
-    .byte 0x92
-    .byte 0xcf
-    .byte 0
-gdt32_end: