ARM: at91: pm: save ddr phy calibration data to securam

The resuming from backup mode is done with the help of bootloader.
The bootloader reconfigure the DDR controller and DDR PHY controller.
To speed-up the resuming process save the PHY calibration data into
SECURAM before suspending (securam is powered on backup mode).
This data will be later used by bootloader in DDR PHY reconfiguration
process. Also, in the process or recalibration the first 8 words of
the memory may get corrupted. To solve this, these 8 words are saved
in the securam and restored by bootloader in the process of PHY
configuration.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210415105010.569620-20-claudiu.beznea@microchip.com