anv: Implement VK_EXT_conditional_rendering for gen 7.5+

anv: Implement VK_EXT_conditional_rendering for gen 7.5+

Conditional rendering affects next functions:
- vkCmdDraw, vkCmdDrawIndexed, vkCmdDrawIndirect, vkCmdDrawIndexedIndirect
- vkCmdDrawIndirectCountKHR, vkCmdDrawIndexedIndirectCountKHR
- vkCmdDispatch, vkCmdDispatchIndirect, vkCmdDispatchBase
- vkCmdClearAttachments

Value from conditional buffer is cached into designated register,
MI_PREDICATE is emitted every time conditional rendering is enabled
and command requires it.

v2: by Jason Ekstrand
  - Use vk_find_struct_const instead of manually looping
  - Move draw count loading to prepare function
  - Zero the top 32-bits of MI_ALU_REG15

v3: Apply pipeline flush before accessing conditional buffer
 (The issue was found by Samuel Iglesias)

v4: - Remove support of Haswell due to possible hardware bug
    - Made TMP_REG_PREDICATE and TMP_REG_DRAW_COUNT defines to
       define registers in one place.

v5: thanks to Jason Ekstrand and Lionel Landwerlin
    - Workaround the fact that MI_PREDICATE_RESULT is not
      accessible on Haswell by manually calculating
      MI_PREDICATE_RESULT and re-emitting MI_PREDICATE
      when necessary.

v6: suggested by Lionel Landwerlin
    - Instead of calculating the result of predicate once - re-emit
      MI_PREDICATE to make it easier to investigate error states.

v7: suggested by Jason
    - Make anv_pipe_invalidate_bits_for_access_flag add CS_STALL
      if VK_ACCESS_CONDITIONAL_RENDERING_READ_BIT is set.

v8: suggested by Lionel
    - Precompute conditional predicate's result to
      support secondary command buffers.
    - Make prepare_for_draw_count_predicate more readable.

Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>