DOCTEAM-2151 core.efi embedded prefix limitation and guidance for multi-environment sub-directory PXE setups

[sounix000]

PR creator: Description

Added a note on core.efi embedded prefix limitation and guidance for multi-environment sub-directory PXE setups.

PR creator: Are there any relevant issues/feature requests?

• bsc#...https://bugzilla.suse.com/show_bug.cgi?id=1257460
• jsc#...https://jira.suse.com/browse/DOCTEAM-2151

PR reviewer: Checklist for editorial review

Apart from the usual checks, please double-check also the following:

• do any new files fulfill the naming conventions specified in https://github.com/SUSE/doc-modular/blob/main/templates/README.md?
• article title/structure title: does it have the required length and does it use sentence style capitalization?
• revhistory: is it up-to-date and does it follow the guidelines specified in https://documentation.suse.com/style/current/html/style-guide-db/sec-smartdocs.html#sec-revhistory?
• backport:
• metadata: does it follow the guidelines specified in https://documentation.suse.com/style/current/html/style-guide-db/sec-smartdocs.html#sec-taglist-smartdocs?