trace: ipc_logging: check for existing ipclog ctxt before creating new one

Many ipc logging clients does a complete driver reinitialization during
shutdown or ssr process. However, these clients prefer to continue use
same logging buffer instead of creating a new buffer. So, check if a
ipc logging context already exist, if so return the same context
instead of creating a new one.

CRs-Fixed: 2214790
Change-Id: Ic0508a0dbf2afbdb1c5d7655c7a79a9bfa01f5a2
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>