[PATCH] doc/linux_gsg: add build instructions for new Arm SoCs

[Thomas Monjalon]

16/05/2025 20:53, Doug Foster:
> Add explanation of recent build configuration changes for Arm SoCs and
> instructions for adding a build configuration for a new Arm SoC.
> 
> Signed-off-by: Doug Foster <doug.foster at arm.com>
> Reviewed-by: Wathsala Vithanage <wathsala.vithanage at arm.com>
> Reviewed-by: Dhruv Tripathi <dhruv.tripathi at arm.com>

Reworded a little to make simpler and avoid the word "recent" in a permanent guide.
Applied, thanks.