target/hppa: Always use copy_iaoq_entry to set cpu_iaoq_[fb]

This will be how we ensure that the IAOQ is always
valid per PSW.W, therefore all stores to these two
variables must be done with this function.

Use third argument -1 if the destination is always dynamic,
and fourth argument NULL if the destination is always static.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>