drm/tegra: Clean up GPIO includes

The Tegra DRM drivers includes the legacy GPIO headers
<linux/gpio.h> and <linux/of_gpio.h> but what it really
uses is <linux/gpio/consumer.h> since only gpio_desc
structs are ever referenced.

Include the right header on the top level tegra/drm.h
file and drop all the surplus includes.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200415122427.111769-1-linus.walleij@linaro.org