radeon: Remove the loop from stride size calculation.

Changed stride size calculation to do the math by rounding
the value instead of loop. r600 minimum stride is 256 which
might might cause up to about 60 rounds of the loop.

src/mesa/drivers/dri/radeon/radeon_mipmap_tree.c

@@ -41,18 +41,24 @@ static unsigned get_aligned_compressed_row_stride(
 		unsigned width,
 		unsigned minStride)
 {
-	const unsigned blockSize = _mesa_get_format_bytes(format);
-	unsigned blockWidth, blockHeight, numXBlocks;
+	const unsigned blockBytes = _mesa_get_format_bytes(format);
+	unsigned blockWidth, blockHeight;
+	unsigned stride;
 
 	_mesa_get_format_block_size(format, &blockWidth, &blockHeight);
-	numXBlocks = (width + blockWidth - 1) / blockWidth;
 
-	while (numXBlocks * blockSize < minStride)
-	{
-		++numXBlocks;
-	}
+	/* Count number of blocks required to store the given width.
+	 * And then multiple it with bytes required to store a block.
+	 */
+	stride = (width + blockWidth - 1) / blockWidth * blockBytes;
+
+	/* Round the given minimum stride to the next full blocksize.
+	 * (minStride + blockBytes - 1) / blockBytes * blockBytes
+	 */
+	if ( stride < minStride )
+		stride = (minStride + blockBytes - 1) / blockBytes * blockBytes;
 
-	return numXBlocks * blockSize;
+	return stride;
 }
 
 static unsigned get_compressed_image_size(