coresight-tpda: Optimize the function of reading element size

Since the new funnel device supports multi-port output scenarios,
there may be more than one TPDM connected to one TPDA. In this
way, when reading the element size of the TPDM, TPDA driver needs
to find the expected TPDM corresponding to the filter source.
When TPDA finds a TPDM or a filter source from a input connection,
it will read the Devicetree to get the expected TPDM's element
size.

Signed-off-by: Tao Zhang <quic_taozha@quicinc.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20241213100731.25914-5-quic_taozha@quicinc.com