ARM: CSR: PM: save/restore irq status in suspend cycle

SiRFprimaII will lose power in deepsleep mode except rtc, pmu and sdram
self-refresh. So IRQ controller will lose status in suspend cyle.
This patch saves irq mask/level registers while suspending and restore
them while resuming.

Signed-off-by: Barry Song <baohua.song@csr.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>