D3D12: Fix out of bounds root parameter index when per-pixel lighting is disabled

[Pokechu22]

ROOT_PARAMETER statically allocates root parameter indexes, but DXContext::CreateGXRootSignature tries to skip ones that aren't relevant (those for bounding box and per-pixel lighting). b6d321b added an additional index for data related to graphics mods, which is always present (even if there are no graphics mods).

However, the logic for choosing what index to use didn't correctly handle per-pixel lighting being disabled, only bounding box being disabled. I've fixed that by moving the graphics mod one to the start of the list, so it doesn't have a dynamic offset. (I think it'd be better to make it optional too, but I'm not confident in my D3D12 abilities to do that right.)

Before:

No per-pixel lighting, no BB:

D3D12 ERROR: ID3D12CommandList::SetGraphicsRootConstantBufferView: RootParameterIndex [9] is out of bounds for the currently set root signature, which declares 9 root parameters. [ EXECUTION ERROR #710: SET_ROOT_CONSTANT_BUFFER_VIEW_INVALID]

No per-pixel lighting, yes BB:

D3D12 ERROR: ID3D12CommandList::SetGraphicsRootConstantBufferView: RootParameterIndex [10] is out of bounds for the currently set root signature, which declares 10 root parameters. [ EXECUTION ERROR #710: SET_ROOT_CONSTANT_BUFFER_VIEW_INVALID]

With per-pixel lighting enabled, this stopped happening. Now, things work properly in both cases.

[dolphin-ci]

FifoCI detected that this change impacts graphical rendering. Here are the behavior differences detected by the system:

• sw3-dt on ogl-lin-mesa: diff

_{^{automated-fifoci-reporter}}