livepatch: Move test-cases to their own sub-directory in test.

livepatch: Move test-cases to their own sub-directory in test.

So they can be shared with ARM64 (but not yet, so they
are only built on x86).

No functional change.

We also need to tweak the MAINTAINERS and .gitignore file.

Also we need to update SUBDIRS to include the new 'test'
directory so 'cscope' can show the example livepatches.

Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com> [arm change]
Acked-by: Jan Beulich <jbeulich@suse.com> [for directory]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>