The Elan I2C touchpad driver is currently manually managing the wake
IRQ. This change removes the explicit enable_irq_wake/disable_irq_wake
and instead relies on the PM subsystem. This is done by calling
dev_pm_set_wake_irq.

i2c_device_probe already calls dev_pm_set_wake_irq when using device
tree, and i2c_device_remove also already calls dev_pm_clear_wake_irq.
There could be some device tree systems that have incorrectly declared
`wake` capabilities, so this change will set the wake irq if one is
missing. This matches the previous behavior.

I tested this on an ACPI system where the touchpad doesn't have _PRW
defined. I verified I can still wake the system and that the wake source
was the touchpad IRQ GPIO.
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Link: https://lore.kernel.org/r/20220929093200.v6.2.Id022caf53d01112188308520915798f08a33cd3e@changeidSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>