eth: fbnic: add locking support for hw stats

eth: fbnic: add locking support for hw stats

This patch adds lock protection for the hardware statistics for fbnic.
The hardware statistics access via ndo_get_stats64 is not protected by
the rtnl_lock(). Since these stats can be accessed from different places
in the code such as service task, ethtool, Q-API, and net_device_ops, a
lock-less approach can lead to races.

Note that this patch is not a fix rather, just a prep for the subsequent
changes in this series.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250410070859.4160768-2-mohsin.bashr@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>