Common: Remove redundant masking in BitField

For the signed case, the shifts already remove the rest of the value, so
ANDing by the mask is redundant.

src/common/bit_field.h

@@ -160,7 +160,7 @@ public:
         if (std::numeric_limits<T>::is_signed)
         {
             std::size_t shift = 8 * sizeof(T)-bits;
-            return (T)(((storage & GetMask()) << (shift - position)) >> shift);
+            return (T)((storage << (shift - position)) >> shift);
         }
         else
         {