[fuchsia] Use the with_source variant of fx_logger_log

fx_logger_log_with_source() takes file and line as parameters
and lets the syslog library handle them.

Change-Id: I15b3b7948e8ad48781ac36afa6fa9df2145da5a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2521365


Commit-Queue: Wez <wez@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824898}