char: hwrng: Add Axxia HW Random number generator

AXXIA TRNG block driver for random number generation has been added.
This provides HW Random number generation using AXXIA HW block. When
enabled in the device tree, /dev/hwrng device is available and random
numbers can be read from there.

Signed-off-by: John Jacques <john.jacques@intel.com>
Signed-off-by: Sreedevi Joshi <sreedevi.joshi@intel.com>
Signed-off-by: Marek Majtyka <marekx.majtyka@intel.com>
Signed-off-by: Charlie Paul <charlie.paul@windriver.com>
Signed-off-by: Daniel Dragomir <daniel.dragomir@windriver.com>