Implemented more arm64 instructions

src/arm/Nop.go

@@ -1,6 +1,6 @@
 package arm
 
 // Nop does nothing. This can be used for alignment purposes.
-func Nop(code []byte) []byte {
-	return append(code, 0x1F, 0x20, 0x03, 0xD5)
+func Nop() uint32 {
+	return 0xD503201F
 }