util/log: Remove qemu_log_close

The only real use is in cpu_abort, where we have just
flushed the file via qemu_log_unlock, and are just about
to force-crash the application via abort.  We do not
really need to close the FILE before the abort.

The two uses in test-logging.c can be handled with
qemu_set_log_filename_flags.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220417183019.755276-32-richard.henderson@linaro.org>