Documentation: dynamic-debug: fix wildcard description

Fix grammar about wildcards and insert a space between sentences.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Will Korteland <will@korte.land>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>