samples: net: gptp: Enable deferred log mode

In applications where timing is critical it seems like enabling
deferred log mode could be desirable.

Signed-off-by: Hake Huang <hake.huang@oss.nxp.com>
Co-authored-by: Seb Laveze <sebastien.laveze@nxp.com>
Signed-off-by: Xabier Marquiegui <xmarquiegui@ainguraiiot.com>

samples/net/gptp/prj.conf

@@ -52,3 +52,5 @@ CONFIG_NET_TC_RX_COUNT=4
 
 # Enable priority support in net_context
 CONFIG_NET_CONTEXT_PRIORITY=y
+
+CONFIG_LOG_MODE_DEFERRED=y