crypto: tcrypt - permit tcrypt.ko to be builtin

When working on crypto algorithms, being able to run tcrypt quickly
without booting an entire Linux installation can be very useful. For
instance, QEMU/kvm can be used to boot a kernel from the command line,
and having tcrypt.ko builtin would allow tcrypt to be executed to run
benchmarks, or to run tests for algorithms that need to be instantiated
from templates, without the need to make it past the point where the
rootfs is mounted.

So let's relax the requirement that tcrypt can only be built as a module
when CONFIG_EXPERT is enabled.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>