docbook: drop z85230 library from kernel-api

Drop z85230 support library info from kernel-api since it's duplicated in
the Z85230 book.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>