hwrng: core - Fix double unlock in rng_dev_read
hwrng: core - Fix double unlock in rng_dev_read

When the loop terminates with size == 0 in rng_dev_read we will
unlock the rng mutex twice.

Reported-by: Dan Carpenter <72501f147b2753e6660fdce744d9ac3084854f5e@gmail.com>
Signed-off-by: Herbert Xu <ef65de1c7be0aa837fe7b25ba9a7739905af6a55@gondor.apana.org.au>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs