Remove unused start() args

bios/stage2.asm

@@ -31,18 +31,9 @@ stage3.entry:
     ; stage3 stack at 448 KiB (512KiB minus 64KiB disk buffer)
     mov esp, 0x70000
 
-    ; push arguments
-    mov eax, thunk.int16
-    push eax
-    mov eax, thunk.int15
-    push eax
-    mov eax, thunk.int13
-    push eax
+    ; push arguments to `start()`
     mov eax, thunk.int10
     push eax
-    xor eax, eax
-    mov al, [disk]
-    push eax
     mov eax, [stage3 + 0x18]
     call eax
     

bios/thunk.asm

@@ -6,18 +6,6 @@ thunk:
     mov dword [.func], .int10_real
     jmp .enter
 
-.int13:
-    mov dword [.func], .int13_real
-    jmp .enter
-
-.int15:
-    mov dword [.func], .int15_real
-    jmp .enter
-
-.int16:
-    mov dword [.func], .int16_real
-    jmp .enter
-
 .func: dd 0
 .esp: dd 0
 .cr0: dd 0
@@ -65,18 +53,6 @@ USE16
     int 0x10
     ret
 
-.int13_real:
-    int 0x13
-    ret
-
-.int15_real:
-    int 0x15
-    ret
-
-.int16_real:
-    int 0x16
-    ret
-
 .pm16:
     ; set segment selectors to protected mode 16-bit
     mov eax, gdt.pm16_data