crypto: aesni-intel - Don't leak memory in rfc4106_set_hash_subkey

There's a small memory leak in 
arch/x86/crypto/aesni-intel_glue.c::rfc4106_set_hash_subkey(). If the call 
to kmalloc() fails and returns NULL then the memory allocated previously 
by ablkcipher_request_alloc() is not freed when we leave the function.

I could have just added a call to ablkcipher_request_free() before we 
return -ENOMEM, but that started to look too much like the code we 
already had at the end of the function, so I chose instead to rework the 
code a bit so that there are now a few labels at the end that we goto when 
various allocations fail, so we don't have to repeat the same blocks of 
code (this also reduces the object code size slightly).

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>