Yes, these alarms are a pain. I don't think there's a way to achieve quite that level of filtering. Some tools offer that sort of granularity, IMC doesn't seem to (yet).
However...it's only the Comware devices generating them. Cisco devices don't generate those particular traps, and you probably never missed them. My advice to people with mixed networks like yours is to just suppress that particular trap.
Instead use Compliance policies to verify that NTP is configured on all your devices. For bonus marks, configure a Compliance policy that logs into the devices, runs "show ntp status" (or equivalent), and then checks that the output shows "synchronized". That's actually a far better level of verification than relying on traps reporting time adjustments.