PM: wakeup: Do not expose 4 device wakeup source APIs

The following 4 APIs are only used by drivers/base/power/wakeup.c
internally.

- wakeup_source_create()
- wakeup_source_destroy()
- wakeup_source_add()
- wakeup_source_remove()

Do not expose them by making them as static functions.

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
Link: https://lore.kernel.org/r/20250420-fix_power-v2-1-9b938d2283aa@quicinc.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>