arm64: zynqmp: Add L2 cache nodes

Linux kernel throws "cacheinfo: Unable to detect cache hierarchy for
CPU 0" warning when booting on zu+ Soc. To fix it add the L2 cache
node and let each CPU point to it.

Reported-by: John Toomey <john.toomey@amd.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/c8dfabab12c97922aaad7fa91be0cbc7e4021528.1688992653.git.michal.simek@amd.com