Update config with kernel v5.17-rc7

This configuration allows building an ACS-IR image with a Linux kernel
updated to v5.17-rc7.

This is of interest for systems supported only by a recent kernel.

We disable the build of Linux bsa, too.
Also, update the documentation.

Suggested-by: G Edhaya Chandran <edhaya.chandran@arm.com>
Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>