ARM: at91/at91sam9x5: PMC header file

Add at91sam9x5 chips family support in PMC header file:
Alternate prescaler location and CSS lenght for PCKR is added.
The new Peripheral Control Register management is added.
Protection mode register is modified to complete its management.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>