net: ethernet: qualcomm: Add PPE driver for IPQ9574 SoC

net: ethernet: qualcomm: Add PPE driver for IPQ9574 SoC

The PPE (Packet Process Engine) hardware block is available on Qualcomm
IPQ SoC that support PPE architecture, such as IPQ9574.

The PPE in IPQ9574 includes six integrated Ethernet MAC for 6 PPE ports,
buffer management, queue management and scheduler functions. The MACs
can connect with the external PHY or switch devices using the UNIPHY PCS
block available in the SoC.

The PPE also includes various packet processing offload capabilities
such as L3 routing and L2 bridging, VLAN and tunnel processing offload.
It also includes Ethernet DMA function for transferring packets between
ARM cores and PPE Ethernet ports.

This patch adds the base source files and Makefiles for the PPE driver
such as platform driver registration, clock initialization, and PPE
reset routines.

Signed-off-by: Luo Jie <quic_luoj@quicinc.com>
Link: https://patch.msgid.link/20250818-qcom_ipq_ppe-v8-3-1d4ff641fce9@quicinc.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>