tcg/tci: Elimnate TARGET_LONG_BITS, target_ulong

We now have the address size as part of the opcode, so
we no longer need to test TARGET_LONG_BITS.  We can use
uint64_t for target_ulong, as passed into load/store helpers.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>