rtc: omap: drop unused dt-bindings header

The definitons in the dt-binding's gpio header only contains some
constants to be used in device trees. It is not relevant for rtc-omap
(as the gpio API hides the details) and in fact unused so it can just be
dropped.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Link: https://lore.kernel.org/r/20200321203737.29850-1-uwe@kleine-koenig.org


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>