drm/i915/selftests: Upgrade printing test/subtest name to pr_info

We're using pr_debug for things that we don't really want to see in the
CI log, but we may find useful during test development.
Let's upgrade the test name printer - we do want to see those in CI log.

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190305144717.10000-1-michal.winiarski@intel.com