ext4: fix memory leaks in error path handling of ext4_ext_zeroout()

ext4: fix memory leaks in error path handling of ext4_ext_zeroout()

commit b720303df7352d4a7a1f61e467e0a124913c0d41 upstream.

When EIO occurs after bio is submitted, there is no memory free
operation for bio, which results in memory leakage. And there is also
no check against bio_alloc() for bio.

Acked-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Jing Zhang <zj.barak@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>