dt-bindings: net: qcom,ethqos: add binding doc for safety IRQ for sa8775p

Add binding doc for safety IRQ. The safety IRQ will be
triggered for ECC(error correction code), DPP(data path
parity), FSM(finite state machine) error.

Signed-off-by: Suraj Jaiswal <quic_jsuraj@quicinc.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>