ARM: CSR: PM: add sleep entry for SiRFprimaII

This patch adds suspend-to-mem support for prima2. It will make prima2
enter DEEPSLEEP mode while accepting PM_SUSPEND_MEM command.

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