turnip: Tell spirv_to_nir that we want fragcoord as a sysval.

Fixes ir3 compiler failure failure in
dEQP-VK.renderpass.dedicated_allocation.formats.r8g8b8a8_unorm.clear.clear_draw
(now just a rendering failure where the subpass clear isn't happening)

Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
1 file changed