target-sparc: on UA2005 don't deliver Interrupt_level_n IRQs in hypervisor mode

As described in Chapter 5.7.6 of the UltraSPARC Architecture 2005,
outstanding disrupting exceptions that are destined for privileged mode can only
cause a trap when the virtual processor is in nonprivileged or privileged mode and
PSTATE.ie = 1. At all other times, they are held pending.

Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
