This makes kernel.bzl smaller.

Test: TH
Test: bazel build //common:kernel_aarch64_dist //gs/google-modules/soc-modules:slider_dist --nobuild
Test: bazel build //build/kernel/kleaf:docs
Bug: 233156052
Change-Id: I28ba7ca430070b57267079e24ebe0e1477f0d9fc
Signed-off-by: Yifan Hong <elsk@google.com>