When a crypto template needs to be instantiated, CRYPTO_MSG_ALG_REQUEST
is sent to crypto_chain.  cryptomgr_schedule_probe() handles this by
starting a thread to instantiate the template, then waiting for this
thread to complete via crypto_larval::completion.

This can deadlock because instantiating the template may require loading
modules, and this (apparently depending on userspace) may need to wait
for the crc-t10dif module (lib/crc-t10dif.c) to be loaded.  But
crc-t10dif's module_init function uses crypto_register_notifier() and
therefore takes crypto_chain.rwsem for write.  That can't proceed until
the notifier callback has finished, as it holds this semaphore for read.

Fix this by removing the wait on crypto_larval::completion from within
cryptomgr_schedule_probe().  It's actually unnecessary because
crypto_alg_mod_lookup() calls crypto_larval_wait() itself after sending
CRYPTO_MSG_ALG_REQUEST.

This only actually became a problem in v4.20 due t...