xsk: Drop ternary operator from xskq_cons_has_entries

Simplify the mentioned helper function by removing ternary operator. The
expression that is there outputs the boolean value by itself.

This helper might be used in the hot path so this simplification can
also be considered as micro optimization.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220413153015.453864-15-maciej.fijalkowski@intel.com