drivers/wifi/espat: Invalid parameter checks lead to system crashes

[hongquan-prog]

Describe the bug
If the system opens the ESP_AT_CIPDINFO_USE option, when the host side
reboot may receive some invalid IPD information (esp32 has not been restarted),
at this time, because the system has just booted up, IPD in the link id does
not exist in the host side, it will execute the following code, but due to the
return value checking logic is incorrect, and continue to use the null pointer
to cause the system to crash.

static int cmd_ipd_parse_hdr(struct esp_data *dev,
			     struct esp_socket **sock,
			     struct net_buf *buf, uint16_t len,
			     int *data_offset, long *data_len)
{
	char ipd_buf[MAX_IPD_LEN + 1];
	char *str;
	char *str_end;
	long link_id;
	size_t frags_len;
	size_t match_len;
	int err;

	......

	*sock = esp_socket_ref_from_link_id(dev, link_id);
	if (!sock) {
		LOG_ERR("No socket for link %ld", link_id);
		return str - ipd_buf;
	}
        
        ......

socket_unref:
	esp_socket_unref(*sock);

	return err;
}

Expected behavior
The system is booting up normally.

Impact
Until the host side restarts esp32, the host side may receive some messages from IPD causing the system to crash

Environment (please complete the following information):

• OS: MacOS
• Toolchain：zephyr-sdk-0.16.4
• Latest main branch