lisa.tests.scheduler.load_tracking: Prefere LITTLE cores in CPUMigrationBase
lisa.tests.scheduler.load_tracking: Prefere LITTLE cores in CPUMigrationBase

LITTLE cores will not be prone to thermal capping, so they are a better choice
if CPU capacities are writeable. Otherwise, pick a big as they will not have
util invariance issues.

ARM-software/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa