tools: Fix ktool build warning
tools: Fix ktool build warning

This patch fixes the following error:
tools/ktool.c: In function ‘load_schema’:
tools/ktool.c:159:20: error: ‘intval’ may be used uninitialized in
this function [-Werror=maybe-uninitialized]
   entry->sensor_id = intval;
   ~~~~~~~~~~~~~~~~~^~~~~~~~
cc1: all warnings being treated as errors

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source