UPSTREAM: coresight: perf: Add helper to retrieve sink configuration

We can always find the sink configuration for a given perf_output_handle.
Add a helper to retrieve the sink configuration for a given
perf_output_handle. This will be used to get rid of the set_buffer()
call back.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(Upstream commit d25054ee8d18c937058a1b69b35fa5bfdef471f3).

Bug: 140266694
Change-Id: I2e069881a090a1a8818bdf237c4f4d8624a3d6e3
Signed-off-by: Yabin Cui <yabinc@google.com>