If anyone includes asm/livepatch.h when CONFIG_LIVEPATCH=n the build
fails with the existing error message. Change it to something saner.

[jkosina@suse.cz: fixed changelog typo spotted by Josh]
Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>