tu: Disable depth and stencil tests when attachment state requires it

The pipeline depth/stencil state can indicate that the stencil test is enabled even in cases where the attachment is missing a stencil component or has a null/unused stencil attachment or format respectively.

Fixes:

dEQP-VK.pipeline.monolithic.stencil.no_stencil_att.*.d24_unorm_s8_uint
dEQP-VK.pipeline.monolithic.stencil.no_stencil_att.*.x8_d24_unorm_pack32

In these tests RB_STENCIL_CONTROL had STENCIL_ENABLE set, causing the stencil test to use wrong values due to the depth format being DEPTH6_24_8 in both.