livepatch: kconfig: use bool instead of boolean

Keyword 'boolean' for type definition attributes is considered deprecated and
should not be used anymore. No functional changes.

Reference: http://lkml.kernel.org/r/cover.1418003065.git.cj@linux.com
Reference: http://lkml.kernel.org/r/1419108071-11607-1-git-send-email-cj@linux.com

Signed-off-by: Christoph Jaeger <cj@linux.com>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>