platform/x86: hp-wmi: Refactor postcode_store() to follow standard patterns

static ssize_t postcode_store(struct device *dev, struct device_attribute *attr,

			      const char *buf, size_t count)

{

	long unsigned int tmp2;

	u32 tmp = 1;

	bool clear;

	int ret;

	u32 tmp;

	ret = kstrtoul(buf, 10, &tmp2);

	if (!ret && tmp2 != 1)

		ret = -EINVAL;

	ret = kstrtobool(buf, &clear);

	if (ret)

		goto out;

		return ret;

	if (clear == false)

		return -EINVAL;

	/* Clear the POST error code. It is kept until until cleared. */

	tmp = (u32) tmp2;

	ret = hp_wmi_perform_query(HPWMI_POSTCODEERROR_QUERY, HPWMI_WRITE, &tmp,

				       sizeof(tmp), sizeof(tmp));

out:

	if (ret)

		return ret < 0 ? ret : -EINVAL;