clocksource: Add devm_clocksource_register_*() helpers

clocksource: Add devm_clocksource_register_*() helpers

Introduce device-managed helpers for clocksource registration.

The clocksource framework currently provides __clocksource_register_scale()
along with convenience wrappers for Hz and kHz registration. However,
drivers must handle error paths and cleanup manually, typically by pairing
registration with an explicit clocksource_unregister() call.

Add a devm-based variant, __devm_clocksource_register_scale(), along with
devm_clocksource_register_hz() and devm_clocksource_register_khz() helpers.

These helpers register the clocksource and attach a devres action to
automatically unregister it on driver detach or probe failure.

This simplifies driver code by:

  * removing explicit cleanup paths
  * ensuring correct teardown ordering
  * aligning with the devm-based resource management model widely used
    across the kernel

While drivers can open-code devm_add_action_or_reset(), providing a
dedicated helper avoids duplication, reduces boilerplate, and ensures
consistent usage across drivers, following patterns used in other
subsystems.

This is also particularly useful for drivers built as modules, where
device-managed resource handling avoids manual cleanup in remove paths and
ensures correct teardown on module unload.

This helper is self-contained and can be adopted progressively by drivers.

No functional change.

Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260506153831.605159-1-daniel.lezcano@oss.qualcomm.com