mboxd: Reduce logging verbosity

Andrew Geissler reported that mboxd was flooding the journal during
boot, making it difficult to track other behaviours in the log.

Fixes openbmc/openbmc#1752

Change-Id: I90d4da42b06fe5a56a399fb849b17f318d6247b5
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/common/recipes-phosphor/mboxd/mboxd/mboxd.service b/common/recipes-phosphor/mboxd/mboxd/mboxd.service
index eab1da8..8adf566 100644
--- a/common/recipes-phosphor/mboxd/mboxd/mboxd.service
+++ b/common/recipes-phosphor/mboxd/mboxd/mboxd.service
@@ -8,7 +8,7 @@
 
 [Service]
 Restart=always
-ExecStart={sbindir}/mboxd --flash {FLASH_SIZE} --verbose --window-size 1M
+ExecStart={sbindir}/mboxd --flash {FLASH_SIZE} --window-size 1M
 
 [Install]
 WantedBy={SYSTEMD_DEFAULT_TARGET}