cputlb: Tidy some macros

TGT_LE and TGT_BE are not size dependent and do not need to be
redefined.  The others are no longer used at all.

Reviewed-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>