net/sfc: fix reading adapter state without locking

net/sfc: fix reading adapter state without locking

Update MAC stats function reads adapter state with MAC stats locking
but without adapter locking. Add adapter locking before calling this
function and remove MAC stats locking since there's no point to have
it together with adapter locking. The second place MAC stats locking
is used is MAC stats reset function. It's called with adapter being
already locked so there's no point to use MAC stats locking anymore.

Fixes: 1caab2f1e68 ("net/sfc: add basic statistics")
Cc: stable@dpdk.org
Signed-off-by: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>