The mbox messages are naturally aligned and in some cases compiler
optimization might disregard natural alignment.
Use volatile key word to force compiler to disable optimizing and
maintain alignment.
Fixes: aecb8e093b52 ("event/octeontx: introduce specialized mbox message copy")
Cc: stable@dpdk.org
Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
Acked-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>