net/mlx5: Fix static checker warnings

For some reason, sparse doesn't like using an expression of type (!x)
with a bitwise | and &.  In order to mitigate that, we use a local variable.

This removes the following sparse complaints on the core driver
(and similar ones on the IB driver too):

drivers/net/ethernet/mellanox/mlx5/core/srq.c:83:9: warning: dubious: !x & y
drivers/net/ethernet/mellanox/mlx5/core/srq.c:96:9: warning: dubious: !x & y
drivers/net/ethernet/mellanox/mlx5/core/port.c:59:9: warning: dubious: !x & y
drivers/net/ethernet/mellanox/mlx5/core/vport.c:561:9: warning: dubious: !x & y

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>