This isn't modified at runtime. Mark it const so it can move to
read-only data.

Cc: dann frazier <dann.frazier@canonical.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240502233447.420888-1-swboyd@chromium.org