For inbound migration we really want to be able to set the PSR without
having any side effects, but cpu_put_psr() calls cpu_check_irqs() which
might try to deliver CPU interrupts. Split cpu_put_psr() into the
no-side-effect and side-effect parts.
This includes reordering the cpu_check_irqs() to the end of cpu_put_psr(),
because that function may actually end up calling cpu_interrupt(), which
does not seem like a good thing to happen in the middle of updating the PSR.
Backports commit 4552a09dd4055c806b7df8c595dc0fb8951834be from qemu
