cputlb: Do unaligned load recursion to outermost function

cputlb: Do unaligned load recursion to outermost function

If we attempt to recurse from load_helper back to load_helper,
even via intermediary, we do not get all of the constants
expanded away as desired.

But if we recurse back to the original helper (or a shim that
has a consistent function signature), the operands are folded
away as desired.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>