ARM: at91: pm: introduce macros for pm mode replacement

Introduce macros to replace standby/suspend mode if they depends on
controllers that failed to map (or other errors). Macros keep track
of the complementary mode to avoid having set the same AT91 PM mode
for both suspend and standby.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>