docs: fix locations of several documents that got moved

The previous patch renamed several files that are cross-referenced
along the Kernel documentation. Adjust the links to point to
the right places.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/m68k/kernel-options.txt

@@ -139,7 +139,7 @@ follows:
   PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF/PARTNROFF=-2
 
 Authoritative information can be found in
-"Documentation/kernel-parameters.txt".
+"Documentation/admin-guide/kernel-parameters.rst".
 
 
 2.2) ro, rw