net/sfc: free MAE lock once switch domain is assigned

net/sfc: free MAE lock once switch domain is assigned

If for some reason the hardware switch ID initialization function fails,
MAE lock is still held after the function finishes. This patch fixes that.

Fixes: 1e7fbdf0ba19 ("net/sfc: support concept of switch domains/ports")
Cc: stable@dpdk.org
Signed-off-by: Viacheslav Galaktionov <viacheslav.galaktionov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>