devargs: fix crash with uninitialized parsing

devargs: fix crash with uninitialized parsing

The function rte_devargs_parse() previously was safe to call with
non-initialized devargs structure as parameter.

When adding the support for the global device syntax,
this assumption was broken.
Restore it by forcing memset as part of the call itself.

Bugzilla ID: 933
Fixes: b344eb5d941a ("devargs: parse global device syntax")
Cc: stable@dpdk.org
Signed-off-by: Madhuker Mythri <madhuker.mythri@oracle.com>
Signed-off-by: Gaetan Rivet <grive@u256.net>