diag: Add PD buffering mode configuration support

This patch extends support to configure buffering
modes for PD buffers by defining new control packets.

CRs-Fixed: 2019180
Change-Id: I5a72ff3ec7e5ab80a7461c3c3130e3b699e75522
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>