hwrng: OMAP: remove SoC restrictions from driver registration

Remove the SoC restriction code from the OMAP RNG driver.  The
integration code in arch/arm/*omap* should handle this.  The device
shouldn't be created if it doesn't exist on the currently-booted SoC.

This allows us to remove some OMAP-specific cpu_is_omap*() calls from
the driver.  Also, if other OMAP chips have RNGs that can be used
by Linux, there will be no need to modify the driver.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>