tcg: don't remove op if output needs to be synced to memory

Commit 9c43b68de628a1e2cba556adfb71c17028eb802e do not correctly check
for dead outputs when they need to be synced to memory in case of
half-dead operations.

Fix that by applying the same pattern than for the default case.

Tested-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
