ShaderGen: Drop DRIVER_V3D and DRIVER_POWERVR macros

They're not needed anymore.

src/util/shadergen.cpp

@@ -210,17 +210,6 @@ void ShaderGen::WriteHeader(std::stringstream& ss, bool enable_rov /* = false */
       if (GLAD_GL_ARB_blend_func_extended)
         ss << "#extension GL_ARB_blend_func_extended : require\n";
     }
-
-    // Test for V3D driver - we have to fudge coordinates slightly.
-    if (std::strstr(reinterpret_cast<const char*>(glGetString(GL_VENDOR)), "Broadcom") &&
-        std::strstr(reinterpret_cast<const char*>(glGetString(GL_RENDERER)), "V3D"))
-    {
-      ss << "#define DRIVER_V3D 1\n";
-    }
-    else if (std::strstr(reinterpret_cast<const char*>(glGetString(GL_RENDERER)), "PowerVR"))
-    {
-      ss << "#define DRIVER_POWERVR 1\n";
-    }
   }
   else if (m_shader_language == GPUShaderLanguage::GLSL)
   {