readme: update readme.md for v1.7 release.

Update the version and remove outdated information.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

README.md

@@ -12,20 +12,20 @@ binaries and pre-compiled topologies for snapshot, stable and LTS releases.
 
 # Installation
 
-The latest SOF release is version 1.6.1 and is available here on the
-stable-v1.6.1 branch. If you want to install this manually instead of from your
-distribution then please follow these instructions
+The latest SOF release is version 1.7 and is available here. If you want to
+install this manually instead of from your distribution then please follow
+these instructions
 
 ```
 git clone https://github.com/thesofproject/sof-bin.git
 cd sof-bin
-git checkout origin/stable-v1.6.1 -b stable-v1.6.1
+git checkout v1.7 -b local/v1.7
 sudo ./go.sh
 ```
 
 alternatively zip and tar files are available to download.
 
-https://github.com/thesofproject/sof-bin/releases/tag/v1.6.1
+https://github.com/thesofproject/sof-bin/releases/tag/v1.7
 
 These files can be uncompressed and the go.sh can be executed as above.
 
@@ -67,11 +67,11 @@ There are four types of SOF releases.
             Deleted immediately upon release of next vendor snapshot. Signed
             with vendor key - less frequent than nightly.
 
-The repository will have a branch for each release e.g. latest vendor snapshots,
+The repository will have a tag for each release e.g. latest vendor snapshots,
 nightlies and stable releases.
 
 ```
-master ----+---> v1.4.2
+main ------+---> v1.4.2
            |
            +---> v1.5.4
            |
@@ -84,29 +84,6 @@ master ----+---> v1.4.2
            +---> lts-20.10
 ```
 
-The master branch will not contain any binaries, but will contain all the tools
-necessary for release management.
-
 It's possible due to release cadence to have several stable branches in the
 repository.
 
-The nightly nightly snapshot branch will have a date tag vDDMMYYYY. The same
-date tag format will be used by vendor snapshots too.
-
-Probably you need to clone a specific branch instead of cloning the default master branch.
-For example, to clone a stable branch, you can do:
-```
-git clone -b stable-v1.4.2 https://github.com/thesofproject/sof-bin.git
-```
-After that, change to the created directory and execute the script:
-```
-sudo ./go.sh
-```
-# Archived Releases
-
-Each release currently takes up about 7MB and would quickly fill up and slow
-down the repository with old data. Therefore SOF stable releases will be also
-available on github whilst nightly and snapshot releases may be available on
-vendor servers (in line with any vendor build/signing cadence). Old release
-branches will be deleted.
-