[comboot] Support COMBOOT in 64-bit builds

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/tests/comboot/shuffle-simple.asm

@@ -0,0 +1,39 @@
+	bits 16
+	org 100h
+
+	jmp start
+
+shuffle_start:
+	push 0xB800
+	pop es
+	mov cx, 80*24*2
+	mov ax, 'AA'
+	xor di, di
+	rep stosw
+.lbl:	jmp .lbl
+shuffle_end:
+	nop
+shuffle_len equ (shuffle_end - shuffle_start + 1)
+
+start:
+	; calculate physical address of shuffled part
+	xor eax, eax
+	push ds
+	pop ax
+	shl eax, 4
+	add ax, shuffle_start
+	mov dword [source], eax
+
+	mov ax, 0012h
+	mov di, shuffle_descriptors
+	mov cx, num_shuffle_descriptors
+	mov ebp, 0x7c00
+	int 22h
+	int3
+
+shuffle_descriptors:
+	dd 0x7C00
+source:	dd 0
+	dd shuffle_len
+
+num_shuffle_descriptors equ 1