samples/ipm: fix markup

Old markup was using %(target)s, which is not the right markup to use,
so it was faiing to build.

Change-Id: Idbe99cfdd695284dc2a66e5823bc65a1417fbfd3
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
1 file changed