fscrypt: remove fscrypt_inherit_context()

Now that all filesystems have been converted to use
fscrypt_prepare_new_inode() and fscrypt_set_context(),
fscrypt_inherit_context() is no longer used.  Remove it.

Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20200917041136.178600-8-ebiggers@kernel.org


Signed-off-by: Eric Biggers <ebiggers@google.com>