hwrng: exynos - Fix runtime PM imbalance on error

pm_runtime_resume_and_get() wraps around pm_runtime_get_sync() and
decrements the runtime PM usage counter in case the latter function
fails and keeps the counter balanced.

Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>