hwrng: imx-rngc - fix the timeout for init and self check

Fix the timeout that is used for the initialisation and for the self
test. wait_for_completion_timeout expects a timeout in jiffies, but
RNGC_TIMEOUT is in milliseconds. Call msecs_to_jiffies to do the
conversion.

Cc: stable@vger.kernel.org
Fixes: 1d544944

 ("hwrng: mx-rngc - add a driver for Freescale RNGC")
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>