hwrng: omap3-rom - Initialize default quality to get data

Similar to commit 62f95ae8 ("hwrng: omap - Set default quality")
we need to initialize the default quality for the RNG to be used.

The symptoms of this problem is that doing hd /dev/random does not
produce much data at all.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Adam Ford <aford173@gmail.com>
Cc: Pali Rohár <pali.rohar@gmail.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>