target/loongarch: Terminate vmstate subsections list

This list requires a NULL terminator.

Fixes: 16f5396cec ("target/loongarch: Add LSX data type VReg")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230510062405.127260-1-richard.henderson@linaro.org>

target/loongarch/machine.c

@@ -163,5 +163,6 @@ const VMStateDescription vmstate_loongarch_cpu = {
     .subsections = (const VMStateDescription*[]) {
         &vmstate_fpu,
         &vmstate_lsx,
+        NULL
     }
 };