perf/arm-cmn: Hide XP PUB events for CMN-600

perf/arm-cmn: Hide XP PUB events for CMN-600

[ Upstream commit 205295c7e1abba9c1db1f9fe075f22f71351887f ]

CMN-600 doesn't have XP events for the PUB channel, but we missed
the appropriate check to avoid exposing them.

Fixes: 60d1504070c2 ("perf/arm-cmn: Support new IP features")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/4c108d39a0513def63acccf09ab52b328f242aeb.1645727871.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>