tci: Convert to new ldst opcodes

Tested-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Remove TCG_TARGET_HAS_new_ldst

Since all backends have been converted, remove the compatibility code.

Acked-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>