common/octeontx2: fix crash on running procinfo

common/octeontx2: fix crash on running procinfo

Segmentation fault has been observed while running procinfo
with reset options i.e. --stats-reset and --xstats-reset.
Reason is procinfo runs as a secondary process and tries to
hold a lock which is part of struct mdev, which was not
allocated as part of shared memory.

Fixes: 5ca59711f771 ("common/octeontx2: add mailbox base support infra")
Cc: stable@dpdk.org
Signed-off-by: Harman Kalra <hkalra@marvell.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>