malloc: do not skip pad on free

malloc: do not skip pad on free

Previously, we were skipping erasing pad because we were
expecting it to be freed when we were merging adjacent
segments. However, if there were no adjacent segments to
merge, we would've skipped erasing the pad, leaving non-zero
memory in our free space.

Fix this by including pad in the erasing unconditionally.

Fixes: e43a9f52b7ff ("malloc: fix pad erasing")
Cc: stable@dpdk.org
Reported-by: Andrew Rybchenko <arybchenko@solarflare.com>
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Tested-by: Andrew Rybchenko <arybchenko@solarflare.com>