boards: mec1501modular_assy6885: Disable KSCAN to avoid test case issues

This change also addresses issue# 21756 tests/obj_tracin where the
expected thread count does not match because kscan module is enabled
in this board. The Microchip kscan driver is contributing to the total
thread count, therefore interfering with the expected test result.

Signed-off-by: Francisco Munoz <francisco.munoz.ruiz@intel.com>