translate-all: fix watchpoints if retranslation not possible

The tb_check_watchpoint function currently assumes that all memory
access is done either directly through the TCG code or through an
helper which knows its return address. This is obviously wrong as the
helpers use cpu_ldxx/stxx_data functions to access the memory.

Instead of aborting in that case, don't try to retranslate the code, but
assume that the CPU state (and especially the program counter) has been
saved before calling the helper. Then invalidate the TB based on this
address.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Alexander Graf <agraf@suse.de>
