hwrng: exynos - Disable runtime PM on probe failure

commit 48a61e1e2af8020f11a2b8f8dc878144477623c6 upstream.

Add proper error path (for disabling runtime PM) when registering of
hwrng fails.

Fixes: b329669e ("hwrng: exynos - Add support for Exynos random number generator")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>