dt-bindings: net/nfc: ti,trf7970a: Add ti,rx-gain-reduction-db option

Add option to reduce the RX antenna gain to be able to reduce the
sensitivity.

Signed-off-by: Paul Geurts <paul.geurts@prodrive-technologies.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250626141242.3749958-2-paul.geurts@prodrive-technologies.com


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