hwrng: mx-rngc - add a driver for Freescale RNGC

The driver is ported from Freescale's Linux git and can be
found in the

	vendor/freescale/imx_2.6.35_maintain

branch.

The driver supports both RNG version C that's part of some Freescale
i.MX3 SoCs and version B that is available on i.MX2x chipsets.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>