wusb: Remove VLA usage of skcipher

In the quest to remove all stack VLA usage from the kernel[1], this
replaces struct crypto_skcipher and SKCIPHER_REQUEST_ON_STACK() usage
with struct crypto_sync_skcipher and SYNC_SKCIPHER_REQUEST_ON_STACK(),
which uses a fixed stack size.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com



Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: Johan Hovold <johan@kernel.org>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: linux-usb@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Git-Commit: d2841f22f4601a2d8bae64ccef7e8e5fa8499e2f
Git-Repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Change-Id: Ic0dedbadc4ed7453c08a7f524f38de098ddc7376
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>