PCIed try to get the PCIed config files from {platform}/plugin/ folder instead of {platform}/ folder

[keboliu]

Description

PCIed is trying to read the pcie.yml file from {platform}/plugin/ folder instead of {platform}/ folder. the plugin folder should be only for the plugins, all the platform related configuration files including pcie.yml should go to {platform}/ folder.

Steps to reproduce the issue:
run the current master image and read the PCIed code will understand that PCIed is expecting the file be placed under plugin folder.

Describe the results you received:

if you put the file under {platform}/ folder which will result in PCIed failed to start.

Jan 11 21:34:03.664365 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:03,663 INFO spawned: 'pcied' with pid 41
Jan 11 21:34:03.880880 r-anaconda-51 ERR pmon#pcied[41]: Platform pcie configuration file doesn't exist! Exiting ...
Jan 11 21:34:03.881122 r-anaconda-51 INFO pmon#/supervisord: pcied Platform PCIe Configuration file doesn't exist!
Jan 11 21:34:03.896688 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:03,896 INFO exited: pcied (exit status 1; not expected)
Jan 11 21:34:04.901144 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:04,900 INFO spawned: 'pcied' with pid 46
Jan 11 21:34:05.048296 r-anaconda-51 ERR pmon#pcied[46]: Platform pcie configuration file doesn't exist! Exiting ...
Jan 11 21:34:05.063223 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:05,062 INFO exited: pcied (exit status 1; not expected)
Jan 11 21:34:07.093888 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:07,093 INFO spawned: 'pcied' with pid 49
Jan 11 21:34:07.249277 r-anaconda-51 ERR pmon#pcied[49]: Platform pcie configuration file doesn't exist! Exiting ...
Jan 11 21:34:07.267095 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:07,266 INFO exited: pcied (exit status 1; not expected)
Jan 11 21:34:09.087807 r-anaconda-51 INFO pmon#/supervisord: message repeated 2 times: [ pcied Platform PCIe Configuration file doesn't exist!]
Jan 11 21:34:11.134432 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:11,133 INFO spawned: 'pcied' with pid 67
Jan 11 21:34:11.286396 r-anaconda-51 ERR pmon#pcied[67]: Platform pcie configuration file doesn't exist! Exiting ...
Jan 11 21:34:11.286640 r-anaconda-51 INFO pmon#/supervisord: pcied Platform PCIe Configuration file doesn't exist!
Jan 11 21:34:11.301085 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:11,300 INFO exited: pcied (exit status 1; not expected)
Jan 11 21:34:11.301299 r-anaconda-51 INFO pmon#supervisord 2021-01-11 21:34:11,301 INFO gave up: pcied entered FATAL state, too many start retries too quickly

Describe the results you expected:

PCIed should change the expecting folder and it should be started successfully with pcie.yml under {platform}/ folder.

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

```
(paste your output here)
```

**Attach debug file `sudo generate_dump`:**

```
(paste your output here)
```