target/ppc: move power-saving interrupt masking out of cpu_has_work_POWER8

target/ppc: move power-saving interrupt masking out of cpu_has_work_POWER8

Move the interrupt masking logic out of cpu_has_work_POWER8 in a new
method, p8_interrupt_powersave, that only returns an interrupt if it can
wake the processor from power-saving mode.

Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Message-Id: <20221011204829.1641124-18-matheus.ferst@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>