arm64: dts: ls1028a: add l1 and l2 cache info

When we ran the stress-ng cache related stressors, we got the log as
below:
ubuntu@ubuntu:~$ stress-ng --l1cache 4
stress-ng: info:  [656] defaulting to a 86400 second (1 day, 0.00 secs) run per stressor
stress-ng: info:  [656] dispatching hogs: 4 l1cache
stress-ng: info:  [657] stress-ng-l1cache: skipping stressor, cannot determine cache level 1 information from kernel

This is because the l1 and l2 cache info is missing in the devicetree,
ls1028a has dual cortex-a72 cores and has 48KB icache, 32KB dcache and
1MB l2 ucache:
  - icache is 3-way set associative
  - dcache is 2-way set associative
  - l2cache is 16-way set associative
  - line size are 64bytes

Signed-off-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>