eth: fbnic: Enable firmware logging

eth: fbnic: Enable firmware logging

The firmware log buffer is enabled during probe and freed during remove.
Early versions of firmware do not support sending logs. Once the mailbox is
up driver will enable logging when supported firmware versions are detected.
Logging is disabled before the mailbox is freed.

Signed-off-by: Lee Trager <lee@trager.us>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250702192207.697368-6-lee@trager.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>