vkd3d-shader/tpf: Write sysval semantic consistently; use the right dcl instruction for sv_isfrontface.

Specifically we should write the sysval semantic as an instruction idx for the following instructions:

VKD3D_SM4_OP_DCL_INPUT_SGV
VKD3D_SM4_OP_DCL_INPUT_PS_SGV
VKD3D_SM4_OP_DCL_INPUT_SIV
VKD3D_SM4_OP_DCL_INPUT_PS_SIV
VKD3D_SM4_OP_DCL_OUTPUT_SIV

and not the following ones:

VKD3D_SM4_OP_DCL_INPUT
VKD3D_SM4_OP_DCL_PS_INPUT
VKD3D_SM4_OP_DCL_OUTPUT

Which is consistent with what we do when reading these instructions in the following functions:

shader_sm4_read_declaration_register_semantic()
shader_sm4_read_dcl_input_ps_siv()

and

shader_sm4_read_dcl_input_ps()
shader_sm4_read_declaration_dst()

for the non-SGV and non-SIV cases.

Note that the non-SGV and non-SIV instructions don't need/use this extra information because they rely on the dst register type and index.

I suggest to introduce this change because the here replaced check is brittle, and we might be omitting the sysval semantic in some cases.

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Additionally 2/2 introduces a fix for the declaration of sv_isfrontface, which native does with dcl_input_ps_sgv instead of dcl_input_ps_siv.