default or selected kernelversion does not have config value CONFIG_NFC_ST21NFCB_I2C.
Result is shown for kernelversion 5.4.229

NFC ST21NFCB i2c support

modulename: st21nfcb_i2c.ko

configname: CONFIG_NFC_ST21NFCB_I2C

Linux Kernel Configuration
└─>Networking support
└─>NFC subsystem support
└─>Near Field Communication (NFC) devices
└─>NFC ST21NFCB i2c support
In linux kernel since version 3.17 (release Date: 2014-10-05)  
This module adds support for the STMicroelectronics st21nfcb i2c interface.
Select this if your platform is using the i2c bus.

If you choose to build a module, it'll be called st21nfcb_i2c.
Say N if unsure.

source code: