ENGR00292341 imx6sl hwrng

ENGR00292341 imx6sl hwrng

Add hwrng support for i.MX6SL.

1. Add RNG driver. This driver originated as fsl-rngc.c. It
   has been modified to support device tree. The name has been
   changed since it supports both b and c variants of RNG.
2. Added clock and compatible info to the device tree data.
3. Added the entry in the options in the Kconfig for hwrng.

(cherry picked from commit 1f3f2c0647b7319c4e23293a61512e4191593513)
[<vicki.milhoan@freescale.com>: Edited to apply to 3.14]

Signed-off-by: Dan Douglass <dan.douglass@freescale.com>
Signed-off-by: Victoria Milhoan <vicki.milhoan@freescale.com>
(cherry picked from commit 586166b87eee2e5ec40331032aed8c8eaec884f3)