drm/omap: include gpio/consumer.h where needed

A lot of the display drivers for OMAP use the gpio descriptor functions
that are only available in linux/gpio.h if GPIOLIB is enabled and
otherwise produce a build error:

drivers/gpu/drm/omapdrm/displays/encoder-opa362.c: In function 'opa362_enable':
drivers/gpu/drm/omapdrm/displays/encoder-opa362.c:101:3: error: implicit declaration of function 'gpiod_set_value_cansleep' [-Werror=implicit-function-declaration]
drivers/gpu/drm/omapdrm/displays/panel-dpi.c: In function 'panel_dpi_probe_pdata':
drivers/gpu/drm/omapdrm/displays/panel-dpi.c:189:23: error: implicit declaration of function 'gpio_to_desc' [-Werror=implicit-function-declaration]
drivers/gpu/drm/omapdrm/displays/panel-sharp-ls037v7dw01.c: In function 'sharp_ls_enable':
drivers/gpu/drm/omapdrm/displays/panel-sharp-ls037v7dw01.c:120:3: error: implicit declaration of function 'gpiod_set_value_cansleep' [-Werror=implicit-function-declaration]

This replaces the existing linux/gpio.h with linux/gpio/consumer.h
where needed. In case of panel-lgphilips-lb035q02.c however, we
also have to include linux/gpio.h to get the definition of gpio_is_valid
and gpio_set_value_cansleep that are used for the non-DT case.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[tomi.valkeinen@ti.com: resolved conflicts]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>