mlx5_core: fix "no space" error on sriov enablement

Change POOL_NEXT_SIZE define value from 0 to BIT(30), since this define
is used to request the available maximum sized flow table, and zero doesn't
make sense for it, whereas many places in the driver use zero explicitly
expecting the smallest table size possible but instead due to this
define they end up allocating the biggest table size unawarely.

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