net: ipc_router: Update debugfs to use seq_file

The debugfs module in ipc_router uses a buffer to dump the data.

Update the debugfs to use seq_files instead of buffers to dump the ipc
router related information.

Change-Id: I6b72c388a6e3ef330c97758f15d4d977fa8aabf7
Signed-off-by: Atish Kumar Patra <apatra@codeaurora.org>