nxp: added csu driver

NXP Central Security Unit(CSU) for NXP SoC.
CSU is used for:
- Access permissions for peripheral that donot have their own
  access control.
- Locking of individual CSU settings until the next POR
- General purpose security related control bits

Refer NXP SoC manuals fro more details.

Signed-off-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Change-Id: I07a4729c79c5e2597f8b2a782e87e09f7f30c2ca
3 files changed