Documentation: admin-guide: kernel-parameters: reformat "lapic=" boot option

Reformat "lapic=" to try to make it more understandable and similar
to the style that is mostly used in this file.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20200918054739.2523-1-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>