iio:temperature:tmp007: Add irq and threshold events support

This patch adds ALERT irq and limit threshold events support for TI TMP007 - 16 bit IR thermopile sensor with integrated
math engine.

Following threshold events are supported:
1. TObj high limit
2. TObj low limit
3. TDie high limit
4. TDie low limit
Signed-off-by: Manivannan Sadhasivam <manivannanece23@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>