hwrng: omap - Don't prefix the probe message with OMAP

So far, this driver was only used for OMAP SoCs. However, if a device
variant is added for an IP block that has nothing to do with the OMAP
platform, the message "OMAP Random Number Generator Ver" is displayed
anyway. Instead of hardcoding "OMAP" into this message, we decide to
only display "Random Number Generator". As dev_info is already
pre-pending the message with the name of the device, we have enough
informations.

Signed-off-by: Romain Perier <romain.perier@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>