maxwell_to_gl: Fix mipmap filtering

OpenGL texture filters follow GL_<texture_filter>_MIPMAP_<mipmap_filter>
but we were using them in the opposite way.

src/video_core/renderer_opengl/maxwell_to_gl.h

@@ -145,7 +145,7 @@ inline GLenum TextureFilterMode(Tegra::Texture::TextureFilter filter_mode,
         case Tegra::Texture::TextureMipmapFilter::None:
             return GL_LINEAR;
         case Tegra::Texture::TextureMipmapFilter::Nearest:
-            return GL_NEAREST_MIPMAP_LINEAR;
+            return GL_LINEAR_MIPMAP_NEAREST;
         case Tegra::Texture::TextureMipmapFilter::Linear:
             return GL_LINEAR_MIPMAP_LINEAR;
         }
@@ -157,7 +157,7 @@ inline GLenum TextureFilterMode(Tegra::Texture::TextureFilter filter_mode,
         case Tegra::Texture::TextureMipmapFilter::Nearest:
             return GL_NEAREST_MIPMAP_NEAREST;
         case Tegra::Texture::TextureMipmapFilter::Linear:
-            return GL_LINEAR_MIPMAP_NEAREST;
+            return GL_NEAREST_MIPMAP_LINEAR;
         }
     }
     }