Fix external surface pitch/slice retrieval.

Change-Id: I21ec9c20a594fd322d17f2bcd1c58b298d4c0ce9
Reviewed-on: https://swiftshader-review.googlesource.com/8812
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/Renderer/Surface.hpp b/src/Renderer/Surface.hpp
index 0f6c220..48e94e1 100644
--- a/src/Renderer/Surface.hpp
+++ b/src/Renderer/Surface.hpp
@@ -514,7 +514,7 @@
 
 	int Surface::getPitchP(bool internal) const
 	{
-		return internal ? getInternalPitchP() : getExternalPitchB();
+		return internal ? getInternalPitchP() : getExternalPitchP();
 	}
 
 	int Surface::getSliceB(bool internal) const
@@ -524,7 +524,7 @@
 
 	int Surface::getSliceP(bool internal) const
 	{
-		return internal ? getInternalSliceP() : getExternalSliceB();
+		return internal ? getInternalSliceP() : getExternalSliceP();
 	}
 
 	Format Surface::getExternalFormat() const