turnip: do not ignore early_fragment_tests

Reenactment of !9569 (merged)

Specifying "early_fragment_tests" in fragment shader takes precedence over our internal conditions.

Fixes test:

 dEQP-VK.fragment_operations.early_fragment.early_fragment_tests_stencil

Fixes: b2a60c15 "turnip: add LRZ early-z support"

CC: @samuelig