Add TGL platform support in README

[Internal]
Platforms: Gen12
OS: Linux
Feature impact: HDCP
Resolves: VSMGWL-23386
Related-to: VSMGWL-23386
Klocwork: PASS
IP Scan: PASS

Change-Id: I40adcd8be7bcd927f7a659aa182a0b57aea062b9