hwrng: omap - Add OMAP4 TRNG support

Add support for OMAP4 version of TRNG module
that is present on OMAP4, AM33xx and OMAP5 SoCs.

The modules have several differences including register
offsets, output size, triggering rng and how configuring
FROs. To handle these differences, a platform_data structure
is defined and contains routine pointers, register offsets. OMAP2
specific routines are prefixed with 'omap2_' and OMAP4
specific routines are prefixed with 'omap4_'.

Note: Few Hard coded values are from the TI AM33xx SDK.
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/Kconfig

@@ -153,12 +153,12 @@ config HW_RANDOM_IXP4XX
 
 config HW_RANDOM_OMAP
 	tristate "OMAP Random Number Generator support"
-	depends on HW_RANDOM && (ARCH_OMAP16XX || ARCH_OMAP2)
+	depends on HW_RANDOM && (ARCH_OMAP16XX || ARCH_OMAP2PLUS)
 	default HW_RANDOM
  	---help---
  	  This driver provides kernel-side support for the Random Number
-	  Generator hardware found on OMAP16xx and OMAP24xx multimedia
-	  processors.
+	  Generator hardware found on OMAP16xx, OMAP2/3/4/5 and AM33xx/AM43xx
+	  multimedia processors.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called omap-rng.