tcg/optimize: fix end of basic block detection

Commit e31b0a7c050711884ad570fe73df806520953618 fixed copy propagation on
32-bit host by restricting the copy between different types. This was the
wrong fix.

The real problem is that the all temps states should be reset at the end
of a basic block. This was done by adding such operations in the switch,
but brcond2 was forgotten (that's why the crash was only observed on 32-bit
hosts).

Fix that by looking at the TCG_OPF_BB_END instead. We need to keep the case
for op_set_label as temps might be modified through another path.

Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
