[HWRNG] omap: Minor updates

Minor cleanups to the OMAP RNG:

 - Comment update re RNG status:
     * yes, it works on 16xx; "rngtest" is quite happy
     * it's fast enough that polling vs IRQ is a non-issue
 - Get rid of BUG_ON
 - Help GCC not be stupid about inlining (object code shrink)
 - Remove "sparse" warning
 - Cope with new hotplug rule requiring "platform:" modalias

And make the file header match kernel conventions.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>