net: macb: Add PM support

This patch
- Adds power management support.
- Updates macb_suspend/resume and runtime_suspend/resume to work in
full power down conditions.
- Adds wake on LAN support using ARP and removes selection of WOL
support via ethtool suing magic packet. This is because ZynqMP PM
support useswake source selection via sys/devices. WOL support is
enabled based on SoC configuration rather than a devicetree property
because this support is specific to IP version and SoC implementation.
- Updates clock init API and fixes clock API header documentation.

Signed-off-by: Harini Katakam <harini.katakam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>