nfc: nci: fix possible NULL pointer dereference in send_acknowledge()

Handle memory allocation failure from nci_skb_alloc() (calling
alloc_skb()) to avoid possible NULL pointer dereference.

Reported-by: 黄思聪 <huangsicong@iie.ac.cn>
Fixes: 391d8a2d

 ("NFC: Add NCI over SPI receive")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20231013184129.18738-1-krzysztof.kozlowski@linaro.org


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