target/hppa: Manage PSW_X and PSW_B in translator

target/hppa: Manage PSW_X and PSW_B in translator

PSW_X is cleared after every instruction, and only set by RFI.
PSW_B is cleared after every non-branch, or branch not taken,
and only set by taken branches.  We can clear both bits with a
single store, at most once per TB.  Taken branches set PSW_B,
at most once per TB.

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