w64: Fix data type of next_tb and tcg_qemu_tb_exec

w64: Fix data type of next_tb and tcg_qemu_tb_exec

next_tb is the numeric value of a tcg target (= QEMU host) address.

Using tcg_target_ulong instead of unsigned long shows this and makes
the code portable for hosts with an unusual size of long (w64).

The type cast '(long)(next_tb & ~3)' was not needed (casting
unsigned long to long does not change the bits, and nor does
casting long to pointer for most (= all non w64) hosts.
It is removed here.

Macro or function tcg_qemu_tb_exec is used to set next_tb.
The function also returns next_tb. Therefore tcg_qemu_tb_exec
must return a tcg_target_ulong.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>