init/fscrypt_init_extensions: remove redundant log message

On every boot, there is a "duplicate" message logged at INFO level for
every system device-encrypted directory, e.g.:

    1     1 I init    : Setting policy on /data/app-private
    1     1 I init    : Encryption policy of /data/app-private set to 3a19970b1aa3abed modes 127/4

Or:

    1     1 I init    : Setting policy on /data/app-private
    1     1 I init    : Verified that /data/app-private has the encryption policy 3a19970b1aa3abed modes 127/4

(Before I51ee70706bc9ccb216ccefd7bdfbbfc57faae14d the second messages
were slightly different, but were similar and still at INFO level.)

The issue is that set_system_de_policy_on() prints its own log message,
then calls fscrypt_policy_ensure() which prints a message too; and the
second message is essentially a superset of the first.

Clean this up by removing the message from set_system_de_policy_on().

Test: Booted and checked the log.
Change-Id: I2786ba7e2dbb355f159ac9d8fe5ad1f0a4cdbfea