common/mlx5: fix default devargs initialization

common/mlx5: fix default devargs initialization

Device arguments list is provided along with its identifier as part of
EAL arguments.
The arguments specified in the list are taken from it, and the rest is
initialized to the default values.

When no list is provided at all, all arguments should have been
initialized to their default values. However, they are mistakenly
initialized to zero which may be a valid value for some.

This patch initializes the default values before checking whether
arguments have been specified.

Bugzilla ID: 945
Fixes: a729d2f093e9 ("common/mlx5: refactor devargs management")

Signed-off-by: Michael Baum <michaelba@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>