net: vrf: move to generic dstat helpers

net: vrf: move to generic dstat helpers

The vrf driver has its own dstats-to-rtnl_link_stats64 collection, but
we now have a generic implementation for dstats collection, so switch to
this.

In doing so, we fix a minor issue where the (non-percpu)
dev->stats->tx_errors value was never collected into rtnl_link_stats64,
as the generic dev_get_dstats64() consumes the starting values from
dev->stats.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240607-dstats-v3-3-cc781fe116f7@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>