msm: ipc: Return error value on send failure

msm_ipc_router_send_msg() returns 0 instead of the error code when the
send helper function fails.

Return error code from helper function in failure cases.

Change-Id: Idef1ceef261945e30b57cd5e99fcb0b2651b31ab
Signed-off-by: Zaheerulla Meer <zmeer@codeaurora.org>