nfc: st21nfca: mark ACPI and OF device ID tables as maybe unused

The driver can match either via OF or ACPI ID tables.  If one
configuration is disabled, the table will be unused:

    drivers/nfc/st21nfca/i2c.c:593:34: warning:
        ‘of_st21nfca_i2c_match’ defined but not used [-Wunused-const-variable=]

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210528124200.79655-11-krzysztof.kozlowski@canonical.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>