fixed sample boot.asm, changed Makefile target to $(ISO)

git-svn-id: svn://anubis/hos/trunk@6 5b3e749e-e535-0410-8002-a9bb6afbdfca

kernel/boot.asm

@@ -18,8 +18,8 @@ multiboot_header:
 	dd	-(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
 
 multiboot_entry:
-	mov byte [0xB8000+160*10+2*2], 'J'
-	mov byte [0xB8001+160*10+2*2+1], 0x07
+	mov ax, 0x0700 + 'J'
+	mov [0xB8000+160*10+2*2], ax
 
 looplbl:
 	hlt