power: Provide dummy log_suspend_abort_reason() if SUSPEND is disabled

The API to log the suspend reason was introduced with commit 57caa2ad
("power: Adds functionality to log the last suspend abort reason.").
It is called from functions enabled with PM_SLEEP and from functions
enabled with SUSPEND, but only available if SUSPEND is enabled.
This can result in build failures such as the following if PM_SLEEP
is enabled, but SUSPEND is not.

kernel/built-in.o: In function `try_to_freeze_tasks':
process.c:(.text+0x30928): undefined reference to `log_suspend_abort_reason'
drivers/built-in.o: In function `syscore_suspend':
(.text+0x6e250): undefined reference to `log_suspend_abort_reason'
drivers/built-in.o: In function `__device_suspend':
main.c:(.text+0x7a528): undefined reference to `log_suspend_abort_reason'

Fixes: 57caa2ad ("power: Adds functionality to log the last suspend abort reason.")
Signed-off-by: Guenter Roeck <groeck@chromium.org>