fixed example to work on a raspberry pi

[JamesWP]

the linux api to talk to i2c devices requires that the device id be specified by ioctl, otherwise how would it know which device to talk to?!

[komigabor]

I tested this on a Raspberry Pi 4 (with latest Raspberry Pi OS) and can confirm that it works (after resolving conflicts). In contrast with the current version which does not.

Conflict resolution:

• use id struct (this is what marked as conflict)
• assign device address before use

final result:

[...]
    /* Make sure to select BME280_I2C_ADDR_PRIM or BME280_I2C_ADDR_SEC as needed */
    id.dev_addr = BME280_I2C_ADDR_PRIM;

    if (ioctl(id.fd, I2C_SLAVE, id.dev_addr) < 0)
    {
        fprintf(stderr, "Failed to acquire bus access and/or talk to slave.\n");
        exit(1);
    }

    dev.intf = BME280_I2C_INTF;
    dev.read = user_i2c_read;
    dev.write = user_i2c_write;
    dev.delay_us = user_delay_us;
[...]