fix: wait for NFC-A frame availability before reading

[Sped0n]

Problem

nfcaReceive() treated the caller-provided RX length as the expected frame size. In practice that value is the RX buffer capacity. When I_rxe is missed and FIFO fallback is used, this can wait for the FIFO to contain the full buffer capacity instead of just waiting for a received frame.

Change Overview

• Change nfcaReceive() to wait for FIFO availability rather than full RX buffer capacity.
• Keep the original RX length as the maximum number of bytes to read from FIFO.

Testing

No test added due to nfcaReceive() depends on real chip IRQ/FIFO behavior, platformio test -e test_UnitNFC_NanoC6 --upload-port /dev/ttyACM0 --test-port /dev/ttyACM0 show no regression on existing tests (145/145 test cases passed).