docs/arm64: elf_hwcaps: Unify HWCAP lists as description lists

Add a series of blank lines to this document to get consistend rendering as
an RST description list.

Signed-off-by: Martin Liska <mliska@suse.cz>
Link: https://lore.kernel.org/r/d0e576ab-6121-b7d7-da5b-7750f05ca7f4@suse.cz


Signed-off-by: Jonathan Corbet <corbet@lwn.net>