TextureCache: Don't lock freed rendertargets for one frame.

New Super Mario Bros on PAL still renders at 60 fps, but skips every 5th XFB copy.
So our detection of "per frame" fails, and we require twice the amound of texture objects.
But our pool frees unused textures after 3 frames, so half of them needs to be reallocated
every few frames.

This commit removes the lock for render targets. It was introduced to not update a texture
while it is still in use. But render targets aren't updated while rendering, so this
lock isn't needed. Non-rendertarget textures however aren't as dynamic, so the lock should
have no performance update.

Source/Core/VideoCommon/TextureCacheBase.cpp

@@ -36,8 +36,8 @@
 #include "VideoCommon/VideoConfig.h"
 
 static const u64 TEXHASH_INVALID = 0;
-static const int TEXTURE_KILL_THRESHOLD =
-    64;  // Sonic the Fighters (inside Sonic Gems Collection) loops a 64 frames animation
+// Sonic the Fighters (inside Sonic Gems Collection) loops a 64 frames animation
+static const int TEXTURE_KILL_THRESHOLD = 64;
 static const int TEXTURE_POOL_KILL_THRESHOLD = 3;
 static const int FRAMECOUNT_INVALID = 0;
 
@@ -1374,9 +1374,11 @@ TextureCacheBase::FindMatchingTextureFromPool(const TCacheEntryConfig& config)
   // Find a texture from the pool that does not have a frameCount of FRAMECOUNT_INVALID.
   // This prevents a texture from being used twice in a single frame with different data,
   // which potentially means that a driver has to maintain two copies of the texture anyway.
+  // Render-target textures are fine through, as they have to be generated in a seperated pass.
+  // As non-render-target textures are usually static, this should not matter much.
   auto range = texture_pool.equal_range(config);
   auto matching_iter = std::find_if(range.first, range.second, [](const auto& iter) {
-    return iter.second->frameCount != FRAMECOUNT_INVALID;
+    return iter.first.rendertarget || iter.second->frameCount != FRAMECOUNT_INVALID;
   });
   return matching_iter != range.second ? matching_iter : texture_pool.end();
 }