removed the integer and bits scaling in quantized bits for alpha=auto and alpha=auto_po2

[fabrizioaymone]

In the quantized_bits class, when alpha=auto or alpha=auto_po2, the unquantized value "x" is manipulated in a strange way. Even if the number of integer bits is not considered when scaling with alpha=auto and alpha=auto_po2, "x" is divided by m_i (, namely 2**integer_bits) to be later remultiplied by the same value m_i. As x is originally divided by m_i, z (which depends on x) is later multiplied by m_i and divided by m. In order to adjust for the division by m, the scale factor (which multiplies z) is multiplied by m.

I removed the m_i and m references in the code as they don't matter when considering alpha=auto or alpha=auto_po2. I also tested this new version of the quantizer with older versions and the result is the same.

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