target/hppa: Split PSW X and B into their own field

target/hppa: Split PSW X and B into their own field

Generally, both of these bits are cleared at the end of each
instruction.  By separating these, we will be able to clear
both with a single insn, instead of 2 or 3.

Reviewed-by: Helge Deller <deller@gmx.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>