forked from Mirrors/opensbi

Currently, the platform's timer device is tracked in two places: the core SBI implementation has `timer_dev`, and the FDT timer layer has `current_driver`. The latter is used for warm initialization of the timer device. However, this warm init is not specific to FDT-based platforms; other platforms call exactly the same functions from the same point in the boot sequence. The code is simplified and made common across platforms by treating warm init and exit as properties of the driver, not the platform. Then the platform's only role is to select and prepare a driver during cold boot. For now, only add a .warm_init hook, since none of the existing drivers need an .exit hook. It could be added in the future if needed. Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Reviewed-by: Anup Patel <anup@brainfault.org>