ext4: ext4_encrypted_zeroout: fix merge error with duplicated call

In ext4_encrypted_zeroout(), submit_bio_wait() gets called twice in a
row.  This seems to be a merge error between commit bd425361 ("ext4
crypto: add ext4 encryption facilities") and c9e01ad4 ("ext4 crypto:
fix bugs in ext4_encrypted_zeroout()")

Remove the duplicated call.

Cc: Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Cc: Ildar Muslukhov <ildarm@google.com>
Cc: "Theodore Ts'o" <tytso@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>