apparmor: use SHASH_DESC_ON_STACK

When building the kernel with clang, the compiler fails to build
security/apparmor/crypto.c with the following error:

    security/apparmor/crypto.c:36:8: error: fields must have a constant
    size: 'variable length array in structure' extension will never be
    supported
                    char ctx[crypto_shash_descsize(apparmor_tfm)];
                         ^

Since commit a0a77af1 ("crypto: LLVMLinux: Add macro to remove use
of VLAIS in crypto code"), include/crypto/hash.h defines
SHASH_DESC_ON_STACK to work around this issue. Use it in aa_calc_hash()
and aa_calc_profile_hash().

Change-Id: I7668f8c6440660e7b68afd8aefd066e496f3beb4
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Git-commit: 9814448da7a84dd50b69e4ada2d7d1c042493daf
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>