drivers: qcom: rpmh: write PDC data

In addition to requests that are send to the remote processor, the
controller may allow certain data to be written to the controller for
use in specific cases like wakeup value when entering idle states.
Allow a pass through to write PDC data.

Change-Id: I00d8875c2aa7d7f2a12543e40b14dd7f8f51cb12
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
Signed-off-by: Raju P.L.S.S.S.N <rplsssn@codeaurora.org>