Incorrect clamp (max instead of min) in rfcomm_getopt SO_RFCOMM_FC_INFO reports bogus flow-control credits

Summary

rfcomm_getopt SO_RFCOMM_FC_INFO (rfcomm_upper.c:550-551): fc->tx_cred=max(dlc->rd_txcred,0xff) fc->rx_cred=max(dlc->rd_rxcred,0xff). max() should be min() for downward clamp to uint8_t. max(x,255) returns 255 when x<255 (common: rd_txcred default RFCOMM_CREDITS_DEFAULT=7 -> reported 255 not 7) returns raw x when x>=255 then truncated. Pure data correctness wrong value to userspace no mem-safety impact. Kernel flow control uses rd_txcred/rd_rxcred directly unaffected. Fix: min(dlc->rd_txcred,0xff).