net: cnss2: Don't check for NULL before ipc_log_string()

The ipc_log_string() function quietly checks for a NULL context so an
explicit check is not needed.

Change-Id: Ic0dedbadf05d153614e1c6a2d3c6f0a536310707
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>