fix intermediate size restriction

Author: jsiek

book.tex

@@ -4082,7 +4082,8 @@ \section{Patch Instructions}
 \end{lstlisting}
 
 There is a similar corner case that also needs to be dealt with. If
-one argument is an immediate integer larger than $2^{16}$ and the
+one argument is an immediate integer larger than $32$ bits (either
+greater or equal to $2^{31}$ or less than $-2^{31}$) and the
 other is a memory reference, then the instruction is invalid.  One can
 fix this, for example, by first moving the immediate integer into
 \key{rax} and then using \key{rax} in place of the integer.