ASoC: cros_ec_codec: remove null pointer dereference warning

Cppcheck complains of a possible issue:

sound/soc/codecs/cros_ec_codec.c:98:10: warning: Possible null pointer
dereference: in [nullPointer]
  memcpy(in, msg->data, insize);
         ^
sound/soc/codecs/cros_ec_codec.c:162:34: note: Calling function
'send_ec_host_command', 5th argument 'NULL' value is 0
       (uint8_t *)&p, sizeof(p), NULL, 0);
                                 ^
sound/soc/codecs/cros_ec_codec.c:98:10: note: Null pointer dereference
  memcpy(in, msg->data, insize);
         ^

In practice the access to the pointer is protected by another
argument, but this is likely to fool other static analysis tools. Add
a test to avoid doing the memcpy if the pointer is NULL or the size is
zero.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20210312182246.5153-5-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/cros_ec_codec.c

@@ -94,7 +94,7 @@ static int send_ec_host_command(struct cros_ec_device *ec_dev, uint32_t cmd,
 	if (ret < 0)
 		goto error;
 
-	if (insize)
+	if (in && insize)
 		memcpy(in, msg->data, insize);
 
 	ret = 0;