fsave: mask fpu cs/opcode (amd)

tests/nasm/fsave_frstor.asm

@@ -8,5 +8,6 @@ global _start
     fsave [esp]
     frstor [esp]
     mov dword [esp + 12], 0 ; fpu eip (currently not emulated)
+    mov dword [esp + 16], 0 ; fpu cs/opcode (currently not emulated)
 
 %include "footer.inc"