docs/sphinx: Fix syntax issues in exclude-list.rst

docs/sphinx: Fix syntax issues in exclude-list.rst

sphinx-build reports:

  docs/misra/exclude-list.rst:50: WARNING: Inline emphasis start-string without end-string.

'*' either needs escaping, or put in a literal block.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
(cherry picked from commit ab03b284b4f2fbf405fcd821105c85e1a38d314d)