drivers: mipi_dbi: spi: add tearing effect support

Add tearing effect support for better display synchronization. This
allows users to configure an external interrupt on falling/rising edges
of the gpio connected to the display controllers tearing effect pin.
See dt-bindings/mipi_dbi/mipi_dbi.h for details of how this works for
mipi_dbi display interfaces.

Signed-off-by: Christian Rask <christianrask2@gmail.com>