Common: Add alignment header

Gets rid of duplicated alignment code.

Source/Core/VideoBackends/D3D12/D3DUtil.h

@@ -7,7 +7,6 @@
 #include <memory>
 #include <string>
 
-#include "Common/MathUtil.h"
 #include "VideoBackends/D3D12/D3DState.h"
 #include "VideoBackends/D3D12/D3DStreamBuffer.h"
 
@@ -19,11 +18,6 @@ extern StateCache gx_state_cache;
 
 namespace D3D
 {
-constexpr unsigned int AlignValue(unsigned int value, unsigned int alignment)
-{
-  return (value + (alignment - 1)) & ~(alignment - 1);
-}
-
 void ResourceBarrier(ID3D12GraphicsCommandList* command_list, ID3D12Resource* resource,
                      D3D12_RESOURCE_STATES state_before, D3D12_RESOURCE_STATES state_after,
                      UINT subresource);