UPSTREAM: coresight: perf: Add "sinks" group to PMU directory

Add a "sinks" directory entry so that users can see all the sinks
available in the system in a single place.  Individual sink are added
as they are registered with the coresight bus.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(Upstream commit 988036f9d322cbd787d8f6a776dbe903d05bae22).

Bug: 140266694
Change-Id: Ida34e7f137b9d7e9094e603408ed7cca8be0fbd5
Signed-off-by: Yabin Cui <yabinc@google.com>