Allow the use of multiple pn532_i2c RFID readers

**Describe the problem you have/What new integration you would like**

I would like to use multiple pn532_i2c devices on a single esp32 device to implement a game.
At the moment the pn532_i2c component only allows a single reader device and it is not possible to define multiple devices.

**Please describe your use case for this integration and alternatives you've tried:**

A single device works as expected:
```
pn532_i2c:
id: rfid1
update_interval: 1s
i2c_id: i2c0
```

Defining multiple devices returns an error `Failed config: expected a dictionary`
```
pn532_i2c:
- id: rfid1
update_interval: 1s
i2c_id: i2c0
- id: rfid2
update_interval: 1s
i2c_id: i2c1
```

**Additional context**

When I look at https://github.com/esphome/issues/issues/3439 and https://github.com/esphome/esphome/pull/3989, it seems adding the requested feature might seem rather trivial?

Start by reviewing the pn532_i2c component configuration and the examples in this request, then consult issues/3439 and PR/3989. Determine how multiple readers should be declared on one ESP32 using i2c0 and i2c1, and verify that both configurations are accepted without the expected-a-dictionary error.

Written by the indexing model from the issue text.