crypto: octeon - don't disable bottom half in octeon-md5

Don't disable bottom half while the crypto engine is in use, as it
should be unnecessary: All kernel crypto engine usage is wrapped with
crypto engine state save/restore, so if we get interrupted by softirq
that uses crypto they should save and restore our context.

This actually fixes an issue when running OCTEON MD5 with interrupts
disabled (tcrypt mode=302). There's a WARNING because the module is
trying to enable the bottom half with irqs disabled:

[   52.656610] ------------[ cut here ]------------
[   52.661439] WARNING: CPU: 1 PID: 428 at /home/aaro/git/linux/kernel/softirq.c:150 __local_bh_enable_ip+0x9c/0xd8()
[   52.671780] Modules linked in: tcrypt(+)
[...]
[   52.763539] [<ffffffff8114082c>] warn_slowpath_common+0x94/0xd8
[   52.769465] [<ffffffff81144614>] __local_bh_enable_ip+0x9c/0xd8
[   52.775390] [<ffffffff81119574>] octeon_md5_final+0x12c/0x1e8
[   52.781144] [<ffffffff81337050>] shash_compat_digest+0xd0/0x1b0

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>