net: ethernet: qualcomm: Initialize PPE buffer management for IPQ9574

net: ethernet: qualcomm: Initialize PPE buffer management for IPQ9574

The BM (Buffer Management) config controls the pause frame generated
on the PPE port. There are maximum 15 BM ports and 4 groups supported,
all BM ports are assigned to group 0 by default. The number of hardware
buffers configured for the port influence the threshold of the flow
control for that port.

Signed-off-by: Luo Jie <quic_luoj@quicinc.com>
Link: https://patch.msgid.link/20250818-qcom_ipq_ppe-v8-4-1d4ff641fce9@quicinc.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>