Fix a typo in iconv.tex

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>

newlib/libc/iconv/iconv.tex

@@ -1095,7 +1095,7 @@ is no corresponding CCS code (error, wrong input data). Else, fetch the
 @item Calculate the offset of the @emph{X} code in its block: 
 @emph{Xindex = Y & 0xFF}
 
-@item If the @emph{Xintex}-th element of the block (which is equivalent to
+@item If the @emph{Xindex}-th element of the block (which is equivalent to
 @emph{from_ucs[BlkN+Xindex]}) value is 0xFF, there is no corresponding
 CCS code (error, wrong input data). Else, @emph{X = from_ucs[BlkN+Xindex]}.
 @end enumerate