crypto: vmx - Fix sleep-in-atomic bugs

This patch fixes sleep-in-atomic bugs in AES-CBC and AES-XTS VMX
implementations. The problem is that the blkcipher_* functions should
not be called in atomic context.

The bugs can be reproduced via the AF_ALG interface by trying to
encrypt/decrypt sufficiently large buffers (at least 64 KiB) using the
VMX implementations of 'cbc(aes)' or 'xts(aes)'. Such operations then
trigger BUG in crypto_yield():

[  891.863680] BUG: sleeping function called from invalid context at include/crypto/algapi.h:424
[  891.864622] in_atomic(): 1, irqs_disabled(): 0, pid: 12347, name: kcapi-enc
[  891.864739] 1 lock held by kcapi-enc/12347:
[  891.864811]  #0: 00000000f5d42c46 (sk_lock-AF_ALG){+.+.}, at: skcipher_recvmsg+0x50/0x530
[  891.865076] CPU: 5 PID: 12347 Comm: kcapi-enc Not tainted 4.19.0-0.rc0.git3.1.fc30.ppc64le #1
[  891.865251] Call Trace:
[  891.865340] [c0000003387578c0] [c000000000d67ea4] dump_stack+0xe8/0x164 (unreliable)
[  891.865511] [c000000338757910] [c000000000172a58] ___might_sleep+0x2f8/0x310
[  891.865679] [c000000338757990] [c0000000006bff74] blkcipher_walk_done+0x374/0x4a0
[  891.865825] [c0000003387579e0] [d000000007e73e70] p8_aes_cbc_encrypt+0x1c8/0x260 [vmx_crypto]
[  891.865993] [c000000338757ad0] [c0000000006c0ee0] skcipher_encrypt_blkcipher+0x60/0x80
[  891.866128] [c000000338757b10] [c0000000006ec504] skcipher_recvmsg+0x424/0x530
[  891.866283] [c000000338757bd0] [c000000000b00654] sock_recvmsg+0x74/0xa0
[  891.866403] [c000000338757c10] [c000000000b00f64] ___sys_recvmsg+0xf4/0x2f0
[  891.866515] [c000000338757d90] [c000000000b02bb8] __sys_recvmsg+0x68/0xe0
[  891.866631] [c000000338757e30] [c00000000000bbe4] system_call+0x5c/0x70

Fixes: 8c755ace ("crypto: vmx - Adding CBC routines for VMX module")
Fixes: c07f5d3d

 ("crypto: vmx - Adding support for XTS")
Cc: stable@vger.kernel.org
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>