ANDROID: Fix race in crng_reseed()

The crng_init triggers process_crng_rdy_callbacks() and those callbacks
can call into the crng again. So, leave the spinlock before processing
the callbacks.

This is a version of upstream commit '4a072c71f49b'

Bug: 124090075
Test: Build and boot cuttlefish with hwrng enabled

Change-Id: Ie5b7a60cd17eae80ca26b518c60110fd18efd548
Signed-off-by: Sandeep Patil <sspatil@android.com>