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>