docs: move asm-annotations.rst into core-api

docs: move asm-annotations.rst into core-api

This one file should not really be in the top-level documentation
directory.  core-api/ may not be a perfect fit but seems to be best, so
move it there.  Adjust a couple of internal document references to make
them location-independent, and point checkpatch.pl at the new location.

Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Joe Perches <joe@perches.com>
Reviewed-by: David Vernet <void@manifault.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20220927160559.97154-6-corbet@lwn.net
Signed-off-by: Jonathan Corbet <corbet@lwn.net>