net/mlx5: do not define static assert in Windows

net/mlx5: do not define static assert in Windows

In Linux 'static_assert' is defined in file mlx5_defs.h:

 #ifndef HAVE_STATIC_ASSERT
    #define static_assert _Static_assert
 #endif

The same definition can originate from Linux file /usr/include/assert.h.

In Windows static_assert is used while _Static_assert is unknown.
Therefore update the definition condition to be:

 #if !defined(HAVE_STATIC_ASSERT) && !defined(RTE_EXEC_ENV_WINDOWS)
    #define static_assert _Static_assert
 #endif

Signed-off-by: Ophir Munk <ophirmu@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>