i2c: add tree.py to parse i2c bus info to tree

The i2c topo is so complex if there are many i2c buses and muxes,
it's hard to understand the i2c bus info from the output of
"i2cdetect -l". This patc

i2c: add tree.py to parse i2c bus info to tree

The i2c topo is so complex if there are many i2c buses and muxes,
it's hard to understand the i2c bus info from the output of
"i2cdetect -l". This patch adds a python script to parse the i2c bus
info to a tree, which is easy to understand.

ps: maybe add a tree view to the i2ctools, but it's not easy to me.

Example:
```
ssh user@<ip> "i2cdetect -l" | python tree.py
root
├── i2c-4
│ ├── i2c-16
│ │ ├── i2c-129
│ │ ├── i2c-130
│ │ ├── i2c-131
│ │ └── i2c-132
│ ├── i2c-17
│ │ ├── i2c-113
│ │ ├── i2c-114
│ │ ├── i2c-115
│ │ ├── i2c-116
│ │ ├── i2c-117
│ │ ├── i2c-118
│ │ ├── i2c-119
│ │ └── i2c-120
│ ├── i2c-18
│ │ ├── i2c-105
│ │ ├── i2c-106
│ │ ├── i2c-107
│ │ ├── i2c-108
....
```

Change-Id: Ia434b093c7ccff80ea52ad7416bcda609890cecd
Signed-off-by: Jian Zhang <zhangjian.3032@bytedance.com>

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