docs-rst: fix broken links to dynamic-debug-howto in kernel-parameters

Another place in lib/Kconfig.debug was already fixed in commit f8998c22
("lib/Kconfig.debug: correct documentation paths").

Fixes: 9d85025b ("docs-rst: create an user's manual book")
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>