meta-romulus: Add led groups for faults

Add fault groups, e.g. core, dimm fault groups in led config, so that
fault monitor could set related fault group to turn on the fault led.

Tested: Verify the led fault groups are created, and when asserted, the
        fault led is turned on.

Change-Id: Iace27d605c11b8c5b3d33685eecdaffb402fc6ad
Signed-off-by: Lei YU <mine260309@gmail.com>