ARM: l2x0: Add aux control register bitfields

This patch adds the PL310 Auxiliary Control Register bitfields
so that SOC's can use these bit fields to construct the AUXCTRL
value to be passed/programmed instead of hardcoding it.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>