seccomp: Fix "cacheable" typo in comments

Do a trivial typo fix: s/cachable/cacheable/

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Cui GaoSheng <cuigaosheng1@huawei.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210331030724.84419-1-cuigaosheng1@huawei.com