Update REAME and diag utility for Nephos (#1100)

- What I did
Add Nephos information into README.md
Update content of npx_diag from binary to shell

- How I did it

- How to verify it
Check npx_diag work as well

- Description for the changelog
Update REAME and diag utility for Nephos

Signed-off-by: Sam Yang <yang.kaiyu@gmail.com>

README.md

@@ -49,6 +49,7 @@ The SONiC installer contains all docker images needed. SONiC uses one image for
 - PLATFORM=mellanox
 - PLATFORM=cavium
 - PLATFORM=centec
+- PLATFORM=nephos
 - PLATFORM=p4
 
 For Broadcom ASIC, we build ONIE and EOS image. EOS image is used for Arista devices, ONIE image is used for all other Broadcom ASIC based devices. 
@@ -91,9 +92,11 @@ This may take a while, but it is a one-time action, so please be patient.
   - docker-orchagent-brcm.gz: docker image for SWitch State Service (SWSS) on Broadcom platform (gzip tar archive)
   - docker-orchagent-cavm.gz: docker image for SWitch State Service (SWSS) on Cavium platform (gzip tar archive)
   - docker-orchagent-mlnx.gz: docker image for SWitch State Service (SWSS) on Mellanox platform (gzip tar archive)
+  - docker-orchagent-nephos.gz: docker image for SWitch State Service (SWSS) on Nephos platform (gzip tar archive)
   - docker-syncd-brcm.gz: docker image for the daemon to sync database and Broadcom switch ASIC (gzip tar archive)
   - docker-syncd-cavm.gz: docker image for the daemon to sync database and Cavium switch ASIC (gzip tar archive)
   - docker-syncd-mlnx.gz: docker image for the daemon to sync database and Mellanox switch ASIC (gzip tar archive)
+  - docker-syncd-nephos.gz: docker image for the daemon to sync database and Nephos switch ASIC (gzip tar archive)
   - docker-sonic-p4.gz: docker image for all-in-one for p4 software switch (gzip tar archive)
 
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