[TF-M] Start of TF-M v1.7.0 release process

Hello,

The branch release/1.7.xhttps://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/log/?h=release/1.7.x has been created indicating the start of the release process and features freeze. RC1 tag will follow after successful run of the basic tests.

Let me remind that the code is not frozen, and development can be continued on the main branch.

Thanks, Anton