ARM: at91: fix ordering of SRAM and PM initialization

The PM initialization needs internal SRAM for allocating a gen_pool and
use it to store its PM code. So we need to have of_platform_populate() before
this code.

Suggested-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>