Input: wistron_btns - use pm_sleep_ptr() to allow removal of ifdef CONFIG_PM guards

Input: wistron_btns - use pm_sleep_ptr() to allow removal of ifdef CONFIG_PM guards

As the guards only apply to suspend and resume, #ifdef CONFIG_PM_SLEEP
would have been a tighter protection. As pm_sleep_ptr() lets the compiler
see the protected ops structure and callbacks but also lets the compiler
remove it as unused code if !CONFIG_PM_SLEEP this allows the #ifdef
guards to be removed, slightly simplifying the resulting code.

--
It seems likely that DEFINE_SIMPLE_DEV_PM_OPS() would work here but
I'd prefer not to make that change unless someone can confirm that the
extra callbacks registered will have no unwanted side effects in this
driver.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20230114171620.42891-17-jic23@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>